In no particular order:
Goodfellas
The Wedding Singer
From Dusk til Dawn (complete with a tattoed George Clooney, back in the days when everyone thought he was straight...
)
For me, your top 3 films have to be ones you'd always be willing to watch again. Hence 3 other films which I think are incredible don't make the list either because they are too sad and if I watch them I end up a horrible teary mess (Dr Zhivago, One Flew over the Cuckoo's Nest) or because they're just too bloody scary (The Shining).