[From MAX-CHEATS.com by BlackDeath for Ghoulboy v2.0.2]

[x99 Lives - lose 1 Life to update]
04000000 00687B40 52800C80

[Invulnerable on - press R-Stick if stuck]
04000000 006879B0 52800008
80000020 
04000000 006879B0 B9406C08
20000000

[Invulnerable off]
04000000 006879B0 B9406C08