These codes work for all 3 home versions of the game (PS2, Xbox, GC):

Invincibility: GMMSKIN
Regenerator: FLSHWND
Unlimited Continues: GRNCHTR
Double HP (Hulk): HLTHDSE
Double HP (Enemies): BRNGITN
1/2 HP (Enemies): MMMYHLP
Reset High Score: NMBTHIH
Level Select: TRUBLVR

The following codes must be entered at a Universal terminal:

SANFRAN (Unlocks Hulk Transformed Art)
PITBULL (Unlocks Hulk vs. Hulk Dogs Art)
FIFTEEN (Unlocks Desert Battle Art)
NANOMED (Unlocks Hulk Movie F/X Art)
JANITOR (Unlocks Gray Hulk)