I have a three worth mentioning. Much like Fred, I always see them in photo pits, and rarely pick them up. One pick was given to me by a friend, one I found on the floor after a show had emptied out, and a Steve Smythe pick from Gigantour that he threw to the crowd that bounced back in the photo pit. I decided to keep that one, much to the disappointment of the people in the front row that almost had it, haha.
The one that was given to me by a friend was Bob Zilla from Damageplan, and the one I found on the floor after a show and kept was Jeff Loomis from the Portland show. I picked it up so the Smythe pick wouldn't be lonely any longer.
Other than that, I don't collect them.