I'm a fan of Keith Hackney for slaying the 500lb sumo, Fry for beating Goodridge + Tank, Frank winning a long hard fought battle against Tito, Marcos Ruas chopping down the Polar Bear, and of course Vitor smashing Ferozzo and Tank. In the first fight there were no gloves. The size differential was astronomical.
Oh and Mad Dog fighting valiantly against Dan Severn. Sadly he got suplexed to death. Total mismatch. That was a one of a kind fight card; David vs Goliath.
Remember Tuli getting his tooth knocked out in UFC 1? In kind of a reversal of what we are talking about here, although Tuli was a lot heavier then the dutch guy Gordeau was known as an absolute killer and feared around the world. Tuli had some nerve getting in the ring with him despite the weight advantage