Pitfall: The Mayan Adventure Cheats (GameBoy Advance)

[L] and [R] are the shoulder buttons. UDLR are directions on the control pad.

  On the title screen, press [L] SELECT A SELECT [R] A [L] SELECT. Now,
  press select and [L] or [R] to cycle through the levels, and press L to begin.

Unlock cheat mode, then start the level of your choice. Hold SELECT and press the D-Pad in
any directly to move freely. Weird!

In order to continue forever, use up all of your lives in the first level, then tap B B B
when the continue screen comes up. The counter will stop counting down and you'll be able
to continue forever.

Unlock cheat mode, then start playing the level of your choice. During gameplay, hold
SELECT and press B to get 99 of each weapon.

Enter this code at the main title screen, to unlock cheat mode: L, SELECT, A, SELECT, R,
A, L, SELECT.