From memory, which means I will have to update this later,
Stuff I have been using for some time:-
Absynth 5 (my old workhorse synth)
Battery 3
Pentagon
Triangle
SFZ (for piano - I purchased an additional sound set)
There should me more stuff on the above list but my memory fails me as it must be five years or more since I was actively "composing."
Stuff I have recently added (and not yet used in anger):-
Guitar Rig 5
Rapture (despite current issues)
Z3ta 2
Session Drummer
BFD Eco
Dimension Pro
Cakewalk Sound Center
Strum Acoustic (A|A|S)
Strum Electric (A|A|S)
Chromaphone (A|A|S)
Ultra Analog (A|A|S)
Tassman 4 (A|A|S)
Lounge Lizard (A|A|S)
String Studio (A|A|S)
The jury is still out on some of the items on the second list. I'm still having issues with Rapture, fir instance, when I try do drive it with Step Sequencer or a MIDI sequence.
I play guitar, sort of, hence trying GR5.
I took a fancy to the A|A|S (Applied-Acoustic Systems) stuff. I started off with Strum Session, which I thought was a gimmicky guitar simulator, but I was quite impressed with some of the sounds it created. There are sampled guitar sounds in Dim Pro, but the "physical modelled" sounds created by Strum Session were much more "natural" in my opinion.
So I then upgrade to Strum Acoustic, and that came as a bundle with Strum Electric. And I was quite impressed, again, but the almost realistic sounds, including the strumming sounds too (upstroke, downstroke, palm mute up, palm mute down, muted and arpeggio). I even experimented with putting GR5 in the effects bin, and I was even further impressed. So expect some real crappy MIDI guitar stuff from me soon...
Anyway, while on the A|A|S website, I was also impressed with the Chromophone (percussion synth) video demo, so at that point, I decided to consider getting the Modelling Collection. Only just scratching the surface of this stuff, but even Lounge Lizard (the electric piano modeller) sounded better than I thought, when it came to some of the Rhodes and different organ sounds.
And I've not finished there. I intend to upgrade to full BFD at some point, and there are a couple more synthetic drum VSTs I fancy getting too.
As for effects... too many to mention, now that I have also recently added all of the latest ProChannel modules (not strictly VSTs I suppose)
The shameful thing about VSTs, for me, is that my hardware is now gathering dust in a corner (Roland JP-8000, Oberheim OB12, Novation Nova, Yamaha A3000 and Korg 0/5RW). If room ever allows in the future, I will hopefully dust them off and integrate them back into the mothership...