Goldeneye 007 on 00 Agent, the hardest difficulty, is tedious as all hell. It involves a lot of aiming a little cursor reticle very, very carefully. If you've never played it, here's how it works: holding R brings up the reticle, but since the N64 only has one stick, you cannot move while you're aiming, and you have to very carefully and accurately move the reticle over the exact pixel of whatever you're trying to shoot. And I mean it when I say "exact pixel", because there are these ceiling-mounted machine guns that'll rip you to shreds in no time, so you have to stay way back and very carefully pick them off. 00 Agent also makes everyone a damage sponge, so you have to squeeze off about a million shots before they explode.
This is on top of the lower ammo count, increased enemy count, and increased damage you take. It is a frustrating, tedious mess. Even Secret Agent (medium) suffers from some of this. I'm all but certain Goldeneye was balanced around Agent (easy) mode.