As a poor student, it's mandatory for me to keep a good stock of beer in the house fridge and a bottle of something in my room.
Quality for quantity is my motto when buying beer. Unfortunately, this usually means buying poor beer on occasions. However, I can usually find a big quantity of Peroni or Tuborg for a good price.
As for harder stuff, I'll drink Jack with coke. There is usually a bottle of Southern Comfort in my room at all times, I'll drink that straight on ice.