From SMS Power!

Cheats: Gunstar Heroes (ガンスターヒーローズ)

Action Replay codes

00C393E7, 00C39403

Begin with 999 Vitality

00C416E7, 00C41703

Infinite Vitality (keeps showing 999)

Game Genie codes

FFC-595-7FB

Start with 255 Health (Vitality)

See the main page for Gunstar Heroes (ガンスターヒーローズ)