I've been thinking of this recently as someone I had thought was a friend, became a flatmate and co-worker too and I realized that I hate their guts :D

A friend for me is intelligent, not necessarily someone with two masters, but street smart too. Someone who challenges me, my thinking, someone who is not afraid of being honest as they know me well enough to know that I might not like what they say, but I will respect them for their honesty. Someone I can respect. Someone who is not insecure and cares way too much about other people's opinion.

A friend is someone who accepts me as I am, and I feel I can be myself completely. Also, someone fun, who is up for trying new things, even for a night out, drinking and clubbing. To consider someone a friend, they have to be really open-minded. Bonus point for dark, sarcastic sense of humour.