I don't believe in pure altruism, and that's not just because I'm a psychopath. From the perspective of evolutionary psychology, a group with altruistic members was more likely to survive than a group with selfish members. Imagine a group of monkeys... Despite that warning their comrades will lead to certain death, Vervet monkeys cry out when they see a predator nearby so their comrades can escape. If the Vervet monkey guard was selfish, the entire group would die, and those monkeys would not pass on their genes of selfishness. Furthermore, among social creatures, the selfish group member is first to be ostracized.

Anyway... If we're talking about acts that have few benefits (or even detrimental effects) for the individual, regardless of group mentality or whatever... Then, yes, I have committed many an altruistic act. I and some of my friends saved a child from an abusive home. I tried to save a man's life when he was in a motorcycle accident (I failed in doing this, but it's the thought that counts). I saved some kittens from being run over, despite running about in the middle of the road and nearly being hit myself. And other things...