Anything by Native Instruments (Reaktor, FM7, Battery, etc.)
Anything by RGC (Z3ta+, Pentagon, etc.)
Anything by Lin Plug, G-media, ReFX, Waldorf, ImageLine, Steinberg, VAZ, Applied Acoustics...............the list goes on and on.
There are so many good VST's out there its easier just to name companies.
If you really wanna get started fast you gotta get Synth1, Crystal, Triangle. Those are dope synths and they're FREE. Theres plenty of free synths out there to get started on. Sometimes I make tracks just with my free shit cuz they sound so good.