strikinglyhandsome1
Sylenth1 - it's depicted on cave drawings.
This is the one I read quite a bit of complaints about with regard to no x64 bit version.
While I've never understood Sylenth1's appeal (it's sound just doesn't do it for me), this is definitely one of the most popular soft-synths out there. The number of third party preset banks for this thing is obscene, and by my estimation, unrivaled.
Not only has it's x64 bit update been a long time coming, but the developer has pretty much disappeared from their support forum at KVR (although, to be fair, he does answer support emails...except for the "when will Sylenth1 be 64 bit?" question).