I learned 5-card Texas Hold-'Em in school, and perfected it on nights 'out' at friends' flats. I then taught my sister. I've still never played with real money - it's not gambling, we just use the chips like monopoly money and play it as a game.
Probably my favourite game at the minute. Dice-chucking worker placement fun, but as with all my favourite games, the thing I like the most is the interaction between the people, superfun times make superfriends.