Extra lives:
Move to the left edge of the screen instead of going through one of the two doors at the "Continue/Quit" screen that appears when a game is over. You will enter a secret room that contains four extra lives.

 

The Adventures of Batman and Robin
Level Skip
To skip the level you're CurrentlY on, press START to pause, then press B, A, Down, B, A, Down, Left, Up, C. ("BAD BAD LUC")

 

 

Level      Password 
Inca       DBBLGLLFCD
Water      DBCLFGBDF2
Jungle     DBDKKJJLKR
Volcano    DBFGCDMBTG 

 

 

Cheat mode:
Press C, A, Right, Left, C, A, Right, Left at the main menu. Begin game play and pause when Aero appears on screen. Press Up, C, Down, B, Left, A, Right, B, then hold A + C to display the cheat menu. Options such as unlimited lives and level select may be enabled.

Unlimited stars:
Enable cheat mode and enter the level selection screen. Press Left, Right, A, B, C, Left, Right, Up, Down, Left, Right.  Press Up and throw a star simultaneously to fly.

 

Bart's Nightmare
Level select:
Quickly press A, B(2), A, Down, Up, Right(2), A while Bart is falling during the opening sequence.
Control other characters:
Complete the game with at least 250,000 and earn an A+ rating. Then, hold Start and press A, B, A, C, B during the ending credits. Other Simpsons characters will be selectable after the game restarts.


BattleTech
Passwords
Level-2:STJNNN
Level-3:GRBCHV
Level-4:BBYLND
Level-5:BMBRMN
Infinite Ammo: BRN521

Beavis and Butt-head
Password
Entire GWAR tickets: XBBEJ JDI-x sVp GD

Bulls V.S. Blazers and the NBA playoffs
Password
Ending: NXWBBBD

Burning Force
Start with Ten Men:

At the title screen, press B, A, B, A, A,C,A,A, then START.

Cyborg Justice
Secret Option Screen
Press START to pause the game, then very quickly press C,B, B,C,C,A,C,B.

Desert Strike
Extra Lives
To begin with 5 lives instead of 3, enter TQQQLOM as your password.

Gunstar Heros
Rotate Logo
Hold Down on Controller 1 before the Gunstar Heroes logo appears to make it rotate.

Sonic The Hedgehog 2
Level select:
Use the sound test selection on the options menu. Choose
sounds 19, 65, 9, and 17 (in that order) and press C after each selection. A chime will confirm correct code entry. Press Start. Hold A and press Start at the title screen.
Super Sonic and Tails:
Enable the "Level select" code. Use the sound test selection on the options screen. Choose sounds 4, 1, 2 and 6 (in that order) and press C after each selection. Music will confirm correct code entry. Select any starting level and collect 50 rings. Sonic or Tails will turn yellow and can run at super speed, jump twice as far, and become invincible to enemies and spikes. The total number of rings will decrease during super mode. Your character will revert to normal when the ring total reaches zero. Note: Super Sonic or Tails can still drown, be crushed, and fall into bottomless pits.
Hyper Sonic:
Run forward in Oil Ocean, Act 2 until reaching the green jet springs. Jump on the very last spring and hold Right. Sonic will hit a group of spikes before becoming stuck in the side of the wall. Jump out to transform into Hyper Sonic. In this mode, Sonic can run faster and jump farther than Super Sonic, but is not invincible.
Mega Sonic:
Collect fifty rings and jump after becoming Hyper Sonic for even more speed and higher jumps.
All Chaos Emeralds:
Enable the "Level select" code. Play songs 4, 1, 2, 6, get 50 rings, and jump.

The Immortal
Password
Final Level- E011F730178C1