Lynch, DiMartini and Vai all use a similar very nice sounding vibrato. I like Timmons as well. I think everyone has clued in to Hammett's lack of vibrato skills but I'll add another name to the bad vibrato list, Steve Morse. He's a great player but his vibrato is in the same league as Hammett's (when I've seen him live anyway). I always thought Jeff Healey had a great unique vibrato too because of the way it was created.