Smoking: gave up for about a month a couple of years back (with patches) then just started again out of boredom...not sure I could do that again any time soon
Drinking: not had a drink for five/six weeks now and I have to say I don't miss it anymore, though i haven't actually spent much time in a pub for a while...I hope I can keep this up!
Wanking: lasted about a week I think, then wondered why I was bothering
Red bull: gave this up for about 3 weeks, maybe the hardest one of all as i was on between two and four cans a day last year, now I probably have one can every other day during the week which feels like a victory to me
Internet: once gave this up for nearly two months, that was hard!
I have a long history of trying to give stuff up, how about you?