Knocking a guy out in Panza Kick Boxing - whatever move you use, it's so satisfying to see him crumple to the floor after smacking him about for ages.
Cannon Fodder - juggling the little enemies about with machine gun fire
Several things in Iron Lord, like winning the arm wrestling contest (a test of real-life speed and strength), getting bullseyes on the archery and killing assasins.
Blowing up loads of men at once with the cannon in North and South.
That'll do for now.