1. Lock, Stock and Two Smoking Barrels - I never get sick of watching it.
2. From Dusk Till Dawn - Enough said
3. Schindler's List - Amazing movie and if you can watch it and not cry yourself into dehydration, kill yourself you emotionless bastard.
That's just 3 that come to mind, I'd never be able to choose in a 'crunch' time situation.