This was almost tricky, because I agree with bmcoll3278 that really zeroing in on 'selfless' is not as easy as we might at first think - we ourselves do benefit in some manner, even merely getting a good feeling, when we simply do 'good deeds' . . . if we think of nice things we've done for others we might initially count that as an act of selflessness, but on further consideration we might well recognize a blessing or comfort we ourselves enjoyed in doing it.
Like, I recall once getting a call in the middle of the night from one of my many daughters that she and her husband were stuck on a highway 50 miles from my house with a flat tire . . . they were about 7 miles from his parents house but he said his parents would never come out at that late hour to rescue them. When my daughter said she then would call me he assured her it was a waste of time and that I too would not come all that way and in the middle of the night to help them - her response was "Of course he will!'. That incident came to my mind first, but only because they (her husband) made such a fuss about the whole thing . . . and the truth is, I was delighted for an opportunity to play the hero fro my daughter, so, it may have been a bit sacrificial, but it was not a selfless act.
But I say this question is 'almost tricky' because as I thought 'can I think of anything at all I ever do that is genuinely selfless, that I don't benefit from at all?' something instantly came to my mind; I kind of regularly feed or set-up humorous remarks or slide answers to questions to others around me, so that they can receive a bit of acclaim or praise . . . in Sunday School classes or small group Bible studies, etc, I will, following the direction of the conversation, say something that offers me up as a goof for someone to wise-crack about - or I'll sort of beat around the bush suggesting terms or names, etc, that prompts another to come-up with answer to a question.
I suppose I do this because I like to see someone, perhaps a seemingly unlikely someone, shine for a moment . . . so, I do gain a mild enjoyment, but I don't feel or sense myself actually benefiting from this in any way, it's not helping me at all in any manner.