Normal, Psychic, an Dragon types dominate Gen 1 for the most part, so I'd go with either Snorlax, Dragonite, Slowbro, or Starmie.
Snorlax has amazing stat distribution and very good power. It requires a lot less prediction than most 'mons and can pretty much plow through anything as long as its packing either Surf or Earthquake. Dragonite just has great stats in general and a huge movepool, and is the best Wrap abuser (back when that move was straight-up broken) even if it gets destroyed by Blizzard.
Slowbro is probably the best Amnesia abuser aside from Mewtwo (this move was crazy good before the Special split), but it's also pretty slow (then again, Thunder Wave helps a lot here). Starmie is much faster and has Recover, but is also a bit frailer, so it could go either way with these two.