I lost in the last tourney I was in with KK. I was in late position and the pot got big to me pre-flop. Big enough to take it right there so I moved all in pre flop. The caller had Ace something suited. No ace came on board but he got his flush on the river.

I've also had it the other way where an Ace does come on board. It is a terrible feeling because some players play any Ace. Like everyone said, it helps to do a big pre-flop raise and get those Ax players out.