If reverse-engineered Nintendo games count, then Super Mario 64 and Pokemon Emerald whose engine is technically open source.
EDIT: Minecraft Beta 1.7.3 has been reverse engineered multiple times too.
If reverse-engineered Nintendo games count, then Super Mario 64 and Pokemon Emerald whose engine is technically open source.
EDIT: Minecraft Beta 1.7.3 has been reverse engineered multiple times too.