I like z3ta+2.
I like Bosch GBH 11 DE
U-HE Zebra 2 and NI Massive
Bosch it’s HAMMER DRILL !!! Ha-Ha!!! Very good!
My roommate is quite the accomplished electronic producer with residencies all over town spinning his tunes and he is in love with both Massive and Sylenth. He squeezes every last inch out of them and his results are spectacular. I’ve never used Sylenth myself but I really enjoy using Massive.
Here is an example of Massive and Sylenth working together on one of his tracks.
http://soundcloud.com/light-speed-to/forever-light-speed-feat-annaAll the best!
U-He Zebra
Albono3, FM8 , Massive. Albino requires less resources, because of this it is number one, in my opinion. reFX (Vanguard, Nexus) and Cakewalk (Z3ta2) synths are pretty nice. Spectrasonics synths are the best but they requires much resources of your computer.
FM8 ,
Pianoteq 
I really like FabFilter Twin 2 and among free ones Kairatune. Nexus was quite useful at times but what I would really like is to get my hands on Omnisphere 
