Call and Response
This is a game of inside jokes that doesn't truly have winners and losers but it can be fun to play with friends. Create a series of responses with the group that you will generate when a person says a particular name or phrase. For instance, if you have a few environmental folk you can have a call be "I love this tree" and the response be "why don't you marry it?" Create more than 20 different calls and responses. To play the game, one player begins with a call and the rest of the group responds emphatically. The player can pass being "it" at any time to someone else and the hilarious calls and responses continue. The game continues as long as you would like it to. You can add new calls and responses to the game as you go along. It may be tough to add a player in the middle of the game but he or she can pick up on it by watching for a bit.
The Memory Game
One player starts by saying, "I am going to a picnic and I'm bringing (some item)." The next player says the same thing, says the item before his and adds another item. The players continue on and on adding more and more items. The items can be wacky and crazy or practical. As the game goes on it will be harder for players to remember. If your group has been drinking, this will be even funnier as it will give you the chance to see who is the most inebriated.
Mafia
Take 12 cards from a deck of cards (or as many cards as are equal to your group size) and include an ace, king, queen, jack and 10. Deal out the cards face-down and tell each player not to reveal what card he received. The king, queen and jack are members of the mafia and the ace and 10 are informants. The rest of the cards are citizens.
If you have more than 12 people, you can use additional cards and add an additional mafia member. If you have between eight and 11 cards, take out one mafia member. For fewer than eight people, take out one additional mafia member. The game does not tend to work as well for fewer than six people.
As the moderator, you explain that each night the mafia will decide to kill somebody and each morning you get to guess who one of the mafia is. Everyone puts their heads down to signify night, then the mafia put their heads up and they motion to the moderator who they want to kill. They put their heads down, then the informants put their heads up and silently guess who is a mafia member, which is either confirmed or denied by the moderator. Everyone puts their heads up and votes on who should be tried for the murder (and killed themselves). The object is to kill the mafia people before they kill all the citizens.
Zombie Capture the Flag
This is just like classic capture the flag except everybody involved is a zombie. This means that there are still two flags and you are still trying to get the other team's flag across to your side without getting tagged, but everybody can only move as fast as a decaying zombie could. Since capture the flag usually takes a degree of running, this makes it so that even out-of-shape or intoxicated people can play. Also, people get to act out the part of a zombie, which can only lead to amusement.
Assassins
Assassins is a game to be played in an office or a college dorm. To "kill" the other members of the game, you must hit them with a plastic spoon or attach a sticky note to them while they aren't looking. The object of the game is to kill the other members of the game before they kill you. This can take place over the course of days or weeks depending on how many people are involved. The winner can receive some sort of prize.