A print-and-play variant of the card game "War" I came up with when I was watching my nephew play the original "War" and it was very obvious he wasn't having a good time with it.

The deck consists of 52 "Sword" cards and 8 "Override" cards, split evenly between two players. Players reveal the top card of their draw pile simultaneously. The player that both swords are pointing at is the loser of that exchange, and the winner places those cards into their capture pile. This continues until someone has no more cards left to play.

"Override" cards alter how the current turn is played, such as your opponent's card becoming your card, forcing them to play a new one.

So, it's War, but instead of being at the complete mercy of random number generation, you do have a bit of an effect on the outcome of a turn. This also has the added bonus of there being way, WAY more "wars" wherein someone could end up losing a ton of cards. It can get to be pretty funny!

Could also be used for conflict resolution in a tabletop game, I suppose.

An attempt to remove the randomness from poker. @mcclure111 gets some of the idea credit.

This is the game, right here:
Each player has one standard deck of playing cards. For each hand, every player secretly draws a five-card hand from their own deck. Three rounds of betting occur, with each player progressively revealing one card of their choice between rounds. After the final round, all unfolded players reveal their remaining two cards and the hand is resolved. Hands are discarded after use, without revealing any still-hidden cards. Memory aids for played cards are allowed, and should be included in computerized implementations. All other rules are the same as standard poker.

SOLITAIRE: THE ROGUELIKE
by Jeremy Penner
version 2.0

Shuffle a deck of regular playing cards. Deal out 25 cards face down in a 5x5 square. Flip the card in the middle so it is face up. This is the dungeon. Deal yourself three cards. These are your starting weapons.

Your goal is to clear out the dungeon of all enemies. To fight an enemy:
- Play one or more cards from the card in your hand on top of a card in the dungeon. If it is face-down, turn it up.
- If the sum of the value of the cards played is less than or equal to the value of the enemy you are fighting, you are killed and the game ends immediately.
- If the sum of the value of the cards played is greater than the value of the enemy you are fighting, you kill the enemy. Discard the cards that you played, and put the enemy card into your hand.
- After the battle is over (and you survive to fight another turn), you do two things:
1. Reveal a card directly adjacent to the enemy that was defeated (no diagonals).
2. Optionally take a card from the top of the deck. If you decide to do so, you must then discard either the card that you just took from the deck, or the enemy card that you just won from the battle.
- If the enemy card was hidden at the beginning of the battle, take an extra new card from the top of the deck.

Jack - 11
Queen - 12
King - 13
Ace - 14
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EDIT: The first version of this game that I posted is painfully degenerate; after the first couple of turns, you were basically so powerful as to be unstoppable (though actually playing that way felt really wrong). This is a vastly improved version that I figured out while my son was in the bath which actually has the player occasionally making interesting choices.