To pick just one game and left rest unmentioned that would be great crime
I can not give name of just one game, there's lot of cool amiga games:
Jaguar, Black Viper, Lotus 3 - fast and smooth race games
Disposable Hero, Agony -shumps
Ruff'n'Tumble, Yo Joe, Lionheart, Brian the Lion, Kid Chaos, Mr Nutz, Turrican 3 -great platform games
and some experimental games like Citadel, sure amiga hardware wasn't made for 3d games but this one play well (as long as screen is small).