Some examples I have heard before are:
-Jessica Lange
-William Shatner (I've heard he will at conventions but is still unfriendly to fans)
-Bruce Willis
-Demi Moore (She was listed on Autograph Collectors Worst IP signers but I have seen a few VV success from her not too long ago. But not many successes and then she switched to secretarial). viewtopic.php?f=125&t=185550 viewtopic.php?f=125&t=188600 http://autographs.keithjakubowski.net/ (Go to the "M" section at the bottom and you'll see scans that were received VV and appear to be authentic).
-Bill Murray
-Tobey Maguire
-Madonna
-Cameron Diaz (I don't want to get in a heated debate over whether her TTM are real or not but I've heard she is very difficult in-person and will only sign if there are cameras on her, like at a premiere or something).
-Britney Spears (I don't know how hard she is but it's probably a matter of actually meeting her through all the security, fans and paparazzi. But maybe she doesn't like to sign? I don't know. Again, I don't know about her TTM).
-Natalie Portman (I have never heard of a ttm or vv success from her and I hear she is very picky even signing IP).
-Joaquin Phoenix (I do know he used to sign TTM and VV but not anymore and is become difficult to get).
-Halle Berry (I heard she was listed on AC's top ten worst in 2008 I believe and that surprised me because I never thought of her to be like that. But she at least sends PP's which are better than nothing or a forgery, right?).
-Alan Alda (According to this link (http://www.foxnews.com/story/0,2933,195331,00.html), he was considered one of the worst which surprises me because he signs TTM but usually signs "one per household."
-Winona Ryder (I have heard she is really hard to get IP and http://autographworld.com/ refers to her as a "Rare" autograph to obtain.
Any others I missed? Thanks!
gghi18
P.S. Here's some links to check out on worst signers and etc...
http://snarkerati.com/celebrity-gossip/ ... h-signers/
http://askville.amazon.com/10-worst-cel ... d=37180147
http://www.foxnews.com/story/0,2933,195331,00.html