Mostly Unpublished Sega Mega Drive / Genesis Cheats ;)

red    marked cheats are unique, not listed on any site (tell me if not).
brown marked cheats from various other sources like gamefaqs.com etc, checked and fixed if necessary.
gray   marked disabled or missed cheats buried inside game ROM.

  California Games
  Fatal Fury 2 (USA), Garou Densetsu 2: Aratanaru Tatakai (Japan)
  Mahjong Cop Ryuu: Shiro Ookami no Yabou
  Shaq-Fu
  Stargate
  Thunder Fox
  ToeJam & Earl in Panic on Funkotron

Cheats summary:

generic cheats	-	1
unique cheats	-	4
buried secrets	-	4
fixed generic cheats	-	3
unverified games	-	1056
games with secrets	-	7
games with no secrets found	-	0
overall progress	-	~1% done

California Games

(UNI) Hidden credits (added 29.10.20):
At the title menu, enter the "SET GAME PARAMETERS" option. Put cursor at the "FOOTBAG:" option and press A, B, C, B, C, A, C, A. There are not only the hidden credits, but the hi-scores of the developers in all game events.

Fatal Fury 2 (USA), Garou Densetsu 2: Aratanaru Tatakai (Japan)

(UNI) Takara logo cheats (added 04.02.21):
At the TAKARA logo screen, input one of following button combination from the table below. Note, the input method is the same as for SPECIAL moves during the game, but with fixed button behavior. When done right, a sound will confirm code triggering. There are not so much time to input the codes, but you actually may input more than one codes sequentially before the title screen appears.

Right, Down + Right, Down, Down + Left + B	-	DIPA bit5. In the Japanese version, enables 4 extra characters at the player selection screen in "VS" game modes. In the US version, these characters are permanently unlocked and corresponding bit in DIPA already set, so cheat won't trigger at the TAKARA logo.
Left, Right, Down + Right, Down, Down + Left, Left, Right + C	-	DIPA bit6. Actual secret cheat sequence. Main effects list is: 1. Activates special COMBO / MAX COMBO counters at the bottom of the game HUD during the game. They are only counts combo and displays the results, nothing more. 2. For "TERRY" unlock secret special move "TRIPLE POWER GEYSER": (in desperation) FORWARD, FORWARD+DOWN, DOWN, BACK+DOWN, BACK + 3D-ATTACK. 3. For "MAI" unlock secret special move "TOE SPIN" (only for arenas "Great Britain", "U.S.A.2" and "Spain"): (tap) 3D-ATTACK x4. 4. For "JUBEI" unlock secret special move "DYNAMITE RICE CRACKER SLIDER": (in desperation) BACK, BACK+DOWN, DOWN, FORWARD+DOWN, FORWARD + 3D-ATTACK. 5. For "CHENG" unlock secret special move "BAKURAI BULLET": (in desperation) BACK, BACK+DOWN, DOWN, FORWARD+DOWN, FORWARD + 3D-ATTACK. 6. Additionally for "JUBEI" TACKLE move (press Mode) adds +4 HP (+2 for each rice cracker eaten).
Down, Down + Left, Left, Down + Left, Right + Y	-	DIPA bit7. Regular known cheat activating two special options : 1. Enables an extra outfit color selection at the player selection screen: hold Start then press B to select the 3rd outfit color. 2. Activates the extra settings editor (DIPB) at the "OPTIONS->TEST" menu. There are set of 8 numbers with values 0 or 1. If we number them from right to left as 0 to 7 (bit0 to bit7 accordingly) the main effects they controlled are follows in the table: bit0 - If set to 1, during the game, on pause, hold any of the following buttons or its combinations then unpause to get a corresponding effect (can be done by any player): A - Enable invincibility. B - Damage miltiplier x2. C - Damage miltiplier x4. B + C - Damage miltiplier x8 (combine B and C). X - Set players health to MIN (1). Y - Set players health to DESPERATION (32). Z - Set players health to MAX (100). bit1 - If set to 1, disables the TACKLE animation break with D-PAD button. bit2 - If set to 1, all DESPERATION special moves are available any time with any HP values. bit3 - If set to 1, activates easy shortcut buttons to trigger DESPERATION special moves for each player. Note, if bit2 set to 0, shortcuts also will work only if HP less or equal 32. Also note, special unlockable 3D-ATTACK buttons shortcurs also available only if DIPA.bit6 is activated. The special shortcuts list is follow: TERRY - MODE + HI-PUNCH - POWER GEYSER MODE + 3D-ATTACK - TRIPLE POWER GEYSER (unlockable, DIPA bit6) ANDY - MODE + HI-KICK - CHO REPPA DAN JOE - MODE + HI-PUNCH - SCREW UPPER KIM - MODE + HI-KICK - HOUOU KYAKU MAI - MODE + HI-KICK - CHO HISATSU SHINOBOBACHI BEAR - MODE + HI-PUNCH - FIRE BREATH MODE + PUCH - SUPER DROP KICK STRENGTH x2 MODE + KICK - SUPER DROP KICK STRENGTH x3 MODE + 3D-MOVE - SUPER DROP KICK STRENGTH x4 MODE + HI-KICK - SUPER DROP KICK STRENGTH x5 MODE + 3D-ATTACK - SUPER DROP KICK STRENGTH x6 JUBEI - MODE + HI-PUNCH - DINAMITE SPINE CRUNCH MODE + 3D-ATTACK - DYNAMITE RICE CRACKER SLIDER (unlockable, DIPA bit6) CHENG - MODE + HI-PUNCH - BAKURAI BOMB MODE + 3D-ATTACK - BAKURAI BULLET (unlockable, DIPA bit6) BILLY - MODE + HI-PUNCH - FLAMING BLAST AXEL - MODE + HI-PUNCH - DASHING PUNCHES BLOOD - MODE + HI-PUNCH - SUPER SABRE SLASH KRAUSER - MODE + HI-PUNCH - KAISER WAVE MODE + 3D_ATTACK - COUNTER HURL ATTACK bit4 - If set to 1, button combination DOWN + 3D-ATTACK from bottom bloor line will cause the roll up to the upper line, i.e. LOW 3D-MOVE. If set to 0, the regular 3D-ATTACK performed instead. Activated by default. bit5 - If set to 1, regeneration timer is counting even if the player is partially stunned or falling down after kick down attacks. Means the opponent have less time to perform chain attacks. Activated by default. bit6 - Similar to bit5 but for other type of attask, like throws (need more investigation). Activated by default. bit7 - If set to 1, when opponent uses a special attack and player is blockng it succesfully, the player need to press BLOCK button (BACK) every time the special attack is performed or else the attack will break the block. Default option here is 0, means if you block the special attack, release BLOCK button does not break the blocking state.

(BUR) Game genie (added 04.01.21):

ABVT-ACDJ (for the US version)	-	Re-enables an unused COLOR test screen. To access it, activate DIPA bit7 cheat first, then enter OPTIONS->TEST menu, put cursor to a line above DIPB settings and press A.
AJ2T-AABW (for the US version)	-	Replaces special TAKARA logo cheat for DIPA bit6 activation with simplier button code: just hold Mode on both controllers, then press C on controller 2.
RFSA-A6V4 (for the US version)	-	Re-enables the funny palette effect at the title screen disabled in the release version.

Mahjong Cop Ryuu: Shiro Ookami no Yabou

(UNI) Secret passwords (added 27.03.19):
There are four types of Mahjong tiles: "numbers" (萬), "barrels" (筒), "ropes" (索) and "honors". In order to input these passwords you need to select the mahjong type with B button, then select the actual tile with either A or C buttons. In the following passwords, the type of the tile described in the second kanji. If there is only one single kanji, then this is a "honor" type tile.

Password	|	Ikari power	|	Skill	|	Luck	|	ESP power	|	Tech level
東、南、西、北、中、發、白、白、一萬、九萬、一筒、九筒、一索、九索	|	100	|	-	|	-	|	-	|	-
一萬、一萬、一萬、二萬、三萬、四萬、五萬、六萬、七萬、八萬、九萬、九萬、九萬、九萬	|	-	|	50	|	50	|	-	|	-
二筒、二筒、三筒、三筒、四筒、四筒、五筒、五筒、六筒、六筒、七筒、七筒、八筒、八筒	|	2	|	-	|	-	|	-	|	2
東、東、南、南、西、西、北、北、中、中、發、發、白、白	|	-	|	-	|	-	|	-	|	10
八萬、四筒、七索、一萬、三筒、七索、中、八萬、四筒、七索、一萬、三筒、七索、二萬	|	1000	|	100	|	100	|	1000	|	20

Shaq-Fu

(FIX) Options screen cheats (added 14.11.20):
Enter the OPTIONS screen. Input one of sequence below the same way you input the special move codes during the game: fast enough with no pauses between buttons because the cheat test routine is the same that used in the game for special moves. THe screen will flash if done right.

A, B, C, C, B, A	-	Blood mode on. Not so much blood thought, this is not a MK after all. Source: gamefaqs.com
A, A, A, A, A, A, A, A, B, B, B, C, C, C, C, C	-	In order to apply this cheat, set MUSIC TEST index to 05 and unplug the controller 2 (if any). Now, plug the controller 2 back if you want, and any time during the fighting in any mode press A + B + C + Left to win instantly. Press A + B + C + Start to return back to the title screen. This work for second controller as well.
Up, Down, B, Left, Right, B	-	Story mode character select. When trigger, the Story mode Character index calculated as a reminder of MUSIC TEST index division by 12. Here is the list of values corresponded to a particular character: 0 = Shaq, 1 = Mephis, 2 = Sett, 3 = Nezu, 4 = Kaori, 5 = Beast, 6 = Auroch, 7 = Voodoo, 8 = Colonel, 9 = Diesel, 10 = Leotsu, 11 = Rajah. So for example, any value below 12 select the exact character, 12 mod 12 is 0 so this means Shaq, as well as 24. 25 mod 12 = 1 so this is Mephis. etc. Source: gamefaqs.com

Stargate

(UNI) Password generator (added 30.01.21):

Stage:
Difficulty:	EasyNormalHard
Hieroglyphs:
Nuclears:
Debug:
Password:

(FIX) Invulnerability (added 30.01.21):
Use the password generator above to generate any password with desired options. Set the "Debug" flag as well. Now, start a game with this password, press Select to enter the Mission Screen, then hold A + C and press Start.
Source: tcrf.net, Mezmorize

Thunder Fox

(GEN) Extra Configuration (added 13.10.20):
Enter the "CONFIGURATION" menu at the title screen, set the "MUSIC" option to "13" and the "SOUND" option to "24", then put cursor to the "EXIT" option and press A, B, C. You'll be able to select the starting stage and number of continues.
Source: gamefaqs.com

(BUR) Test menu (added 13.10.20):
Patch the game ROM at location $093A3 for the US version (or $095B3 for the Japanese version) to value $02 then enter the Extra Configuration mode as described above. Now, put cursor again to "EXIT" and enter A, A, A, A, A, A, A, A, A, B, C, B, A, B, C, B, A, C, A, C, B, A, C, C, A, A, C, B, B, C, C. This is not actually a test menu, but a collection of sound samples one of which is "FUCK YOU ASSHOLE!" for example. No wonder they disabled it from release.
Source: GManiac

(BUR) Debug flag (added 13.10.20):
For any versions, patch the game ROM at location $2FFFF to value $00. Now you'll be able to enter to the Extra Configuration mode simply by entering A, B, C, no need to set the sound test parameters. Also, there are two more options available there. The "JUDGE" option activates the damage taken by the player, turn it "OFF" to invincibility. "THROWING KNIFE" is self-explanatory. The knife turns into throwable weapon with infinite ammo. You don't need the rifle anymore.

(BUR) Region switch (added 13.10.20):
Only for the US version, patch ROM location $2FFFE to value $00 to switch the game to the Japanese version.

ToeJam & Earl in Panic on Funkotron

(FIX) Secret passwords (added 22.01.21):
Enter one of the following words as a password. You may input more than one passwords at a time. A message "BOGUS PASS" does not mean passwords does not work. After input, start a new game or input any valid password to start a game with corresponding effects.

!me9acheat!	-	On a regular levels: press Start to open the ingame pause menu, hold one of corresponding combinations and press A to get a corresponding effect: Hold Left + Down - Level select. Note, when selecting stage 18 with this mode, you select the Ending level. By default this is worst ending. To see all three good endings, add either 1, 2 or 3 to the current password: !me9acheat!1 - Good Ending 1 (Few Items Found) !me9acheat!2 - Good Ending 2 (Many Items Found) !me9acheat!3 - Best Ending 3 (All items Found) Hold Right + Up - Free movement mode.
!rapma5ter!	-	Activates all prizes effects at once permanently for the whole game, including those inaccessible via passwords or in-game: infinite lives and slower clocks.
tj t0ejam earl	-	All shows the same hidden game credits.
mand1 renee janda dave 5ean dan1el 5anda	-	Each shows a corresponding dedication message.
fl199lefr1tz	-	Infinite permanent Air underwater.
perqvacky	-	Invulnerability. You still may be drown.
-m1n9yen-	-	Infinite permanent Super Jars.
!!15778047!!	-	Infinite permanent Funks.
nevernever	-	Infinite permanent Panic Buttons.
--h00ver	-	Infinite permanent Funk Vacuums.
-han9t1me-	-	Instant high jump on Bouncing Fungus.
!5t1ckyfeet	-	No falling off from floating Bubbles.

Source: gamefaqs.com