I'm STILL somewhat mad at my little brother...in my early teens, I had a friend whose Dad was an avid comic collector until his kids came along and none of them had any interest so he gave them all to me.
What comes to mind immediately is a '55 Detective Comics in fair condition (I actually took it out to read it, idiot lol), the XMen series right from when the new XMen are taken in by Mesmero (after the original XMen were taken hostage by that sentient island, Krakoa); the first Wolverine 4 part miniseries, the first Punisher miniseries by Mike Zeck (now THESE were worth something even then) old (for even then, 1980s) Spiderman, FF, DD, Avengers and even older XMen books. There were over 100 in all; not including my own collection. When I moved out of my parents' house, I didn't take them w/me so they ended up giving them to him and then HE gets in trouble and they took them away from him. Where'd they go? No one knows. Burns still, it does.
Of course, I managed to get ahold of some of those ones, copies, from other places but there's no replacing all of it since I don't remember most of'm now.