Alphabeat
No not the terribly poptastic Danish band. The joint top best drinking game ever. Very similar to slaps except with letters of the alphabet instead of numbers. 
Game starts with everyone chanting the following: 'Whats the name of the game? Alphabeat! Whats the object? To learn letters!' Consonants are represented by a slap of the shoulder which also decides the direction, while vowels are represented by putting one hand over the other, with the top hand deciding direction. If someone messes up they drink for the number of seconds that letter represents. i.e. d equals 4 seconds.Instead of counting the seconds though you must count up in letters e.g. A, B, C, D instead of 1,2,3,4.  If someone messes up on 'A' however there is a 10 second drinking penalty. 
Billy, Bob and Timmy (shouting together): Whats the name of the game? Alphabeat! Whats the object? To learn letters!

*Bob taps shoulder for 'A'*

Billy and Timmy Together: AHHHHH wanker! 'A' is a vowel! Drink for 10 seconds

Billy: You're such a retard Bob