Omaha Hold' Em
This is played the same as Texas Hold'Em, with two exceptions.
One, that each player is dealt four cards at the beginning of the game instead of two.
Two, when making one's best five card hand, each player must use exactly three of the five community cards and two of their four hole cards.
The game can be played as per Texas Hold'Em rules (with blinds) or as per Home Hold'Em rules (with antes).
Another home variation is to allow players to use whatever combination of community cards and the hole cards that they want to make their five card hand.