Expansion Pak NUS-007 Nintendo 64 N64

Memory Expansion for Nintendo 64 Console (NUS-007)

Here are the 3 games for which it is essential to have the expansion pak. For the other games, it allows you to play with better resolution or fluidity.

Donkey Kong 64
The Legend of Zelda: Majora's Mask
Perfect Dark: Essential for single player, co-op, and counter-operation mode.