These two items are highlights of my collection, for a couple of different reasons.
Robert Pattinson - this was acquired by a friend of mine from a card collecting forum at the London Film and Comic Con, probably in 2006/7. Why is it a highlight of my collection? Well, take a look at the completed auctions on eBay. Ignore the $30 ones, those are fake. Look at the real ones. See the signature? It's just an R now. This is a full signature, and it's a Harry Potter photo instead of Twilight. This is something you literally could not get these days - after so many signatures, his autograph has devolved into a single letter, and good luck getting close to him.
Elizabeth Henstridge - my friend Lew got this for me at a con in Texas. She's cute as a button, I love the photo and I have grown to really love Agents of S.H.I.E.L.D. after the really great season two. But she's currently doing the convention circuit on a currently airing show, so why is it such a great part of my collection? Same deal as with Robert Pattinson: her signature has changed for the worse. She only signs her first name now, and while there is a chance she will eventually return to the full signature, it probably won't be anytime soon and so I'm happy to have this piece.