Cards Against Humanity is a hilarious game. The box calls it, "a party game for horrible people."
The basic rules are:
Players get 10 white cards.
Each round a judge chooses a black card and reads it aloud to the group. Players then choose their funniest white card. (This is where it gets hilarious, or horrible.)
The judge chooses the card that they like the best.
You can only buy it online.. probably because it offends many people. But I think those people just don't know how to have fun.
This is the website: Cards Against Humanity
Here's the link to buy it: Buy Cards Against Humanity