Believe it or not, there exists a two-player variant of this game, which is also known as Cheat and I Doubt It.
Preparation
Of course, you'll want a standard 52-card deck of playing cards (I guess you could play with jokers, but I don't see the point). The entire deck should be dealt out.
Object of the game
The object of the game is to get rid of all cards in the hand.
Play
The player holding the Ace of Spades must first place that card face-up in the pile. The other player gets 2s. The first player gets 3s and so on like this. From king, it goes back to ace until one player his eliminated all of his cards.
Decisions on the turn
A player may either pass or play a card.
Pass
A player's turn is skipped.
Playing a card
The player will play any number of cards (more than four, however, is not advisable) face-down and announce their number and rank (e.g., "3 tens").
Bluffing
The bluff is an integral part of this game. You obviously won't have the cards you need every time. However, especially in the two-player version, this can be difficult, because the opposing player has two weapons to combat the bluff.
The challenger says "I doubt it," "cheat," or "bullshit." The other player's cards are turned face-up. If the challenged player was bluffing, he must take the entire pile into his hand. However, if the cards are correct, the challenging player must take the pile into his hand.
The challenger says "force." If the challenged player cannot produce a card of the correct rank from his hand, he must take the pile. If he can, however, the challenger must take the pile.
There are some interesting strategies for this game. The first couple times, you'll probably get your friends by claiming to play all four cards of a rank and bluffing—chances are they'll try a force.
You should realize that this game takes a really long time to play and can be grueling.
You can also use these rules with more than two players, if it strikes your fancy.