Flipcup and
beer pong are my two favorite games. All you need there is a table to drink on. I had a rather cheap pool table that I just put a piece of plywood overtop of it and used it.
Card game wise, I like
Asshole because you gain to ability to make someone drink.
A easy game I've played at a party was Port Starboard. Everyone plays the game at the same time and it only has one rule. You must drink with your less dominate hand (ie. if you hold your drink in your right hand normally, you must hold it in your left hand while playing). If someone catches you drinking with your dominate hand, you must finish off what you are drinking. You have to yell "Port Starboard" when you see this.
I say, build a beer pong table. The mods for them are endless and it makes a great discussion piece for your parties. Chicks like it when you know how to build things.