The last comic I gave away was Chilling Adventures of Sabrina #1 to my brother. I eventually replaced it digitally.
Before that, the last comic I gave away... was actually like two or three boxes to a friend when I move a few years ago. He got several signed Green Lantern Rebirths out of it, as well as the first three issues of all the New52 launch, among others.
What was the last comic, or comics, you gave away?