I'll start off by listing mine:

The T-800, Terminator 2: "I know now why you cry, but it's something that I can never do." Gets me every damn time.

ADA, Zone of the Enders: I think I'm the only one who played this game more than the MGS2 demo that came with it. I will never not laugh at the exchange of "You may speak like a human, but you're still a heartless computer, aren't you?" "That is correct. What is the problem?"

Codsworth, Fallout 4: He survives the nuclear holocaust despite not having a bunker and waits 200 years for you to come back. When you look at what changes his relationship with you, he mostly just wants you to be nice to people. I never swapped him out as my companion.

B.O.Y.D., Ducktales 2017: He's adorable. 'nuff said.