No question about it, my favourite line is in Lock Stock and 2 Smoking Barrels at the card game...
"FOLD! Is that the only word they taught you at school Donald... Fold!!??"
"NO PHIL!!!.... They also taught me the word C**t"
Legendary status in my book but possibly not such a favourite for the ladies with the inclusion of that last word! Sorry bout that but it's the icing on the cake for that scene I reckon.