1) Being willing to die for Katherine in 1864 
2) Compelling Stefan’s snacks to stay quiet to protect him
3) Compelling Jeremy in 1x07 
4) Saving Elena in 1x11 
5) Save Stefan mission in 1x17-1x20 
6) Defending Elena to Isobel
7) Trying to create a truce with Bonnie in 1x22-2x01 
8) Giving Caroline his blood in 2x01
9) Taking a wooden arrow for Elena in 2x03 
10) Letting Liz live in 2x05 
11) Defending Caroline to her mom in 2x05 
12) Letting Elena go in 2x08 
13) Giving Rose her dream in 2x12 
14) Helping Stefan save Caroline in 2x13 
15) Helping Bonnie stay alive in 2x18 
16) Not caring about whether or not Elena hates him if it means she’ll live
17) Saving Tyler and Caroline in 2x20 
18) Hiding the bite from Elena so she wouldn’t have to suffer
19) Not telling Elena about his Stefan research so she wouldn’t get her hopes up in 3x01 
20) Pimping out the woman he loves to another man in 3x01-3x09 
21) Compelling Jeremy to leave in 3x10
22) Saving Matt in 3x14
23) Taking the fall for Stefan by killing/turning Abby in 3x15

It’s important to note that on an evolutionary scale, he is superior to humans as a vampire. Any deed that even remotely inconveniences him and/or throws him out of his comfort zone could be considered selfless. If there is no direct personal gain to be acquired through the act, it IS selfless, no matter the circumstances surrounding said act. Damon is not a saint, nor is he a monster. He is something in between, and in order to fully appreciate the nuances in his character, it is important to take both the good and the bad into consideration.