I just recently purchased the vintage ik multimedia compressor suite and so far love them. My question is, I know it comes down to a case by case determination but     in general what are your go to compressors and on what instruments? Thank you

1176 in the prochannel.  I'm not afraid to use it on anything.

1176 and CA-2A that come with Sonar on anything.

I have been using MTurboComp by Melda because it emulates many compressors. 

Presswerk (u-he) because of it's versatility
Valley people dynamite (softube) for smacking the **** out of everything :-)

Klanghelm MJUC, Waves DBX-160 and CA-2A get a lot of love from. One that isn't technically a compressor, but I tend to use it as one and that has become of my most loved plugins is Waves' Infected Mushroom Pusher.

Three come to mind, not mastering comps, but for squashing the crap out of guitars so the bells will ring.
 
Vitamin C, which if free  (hey, rhymes...maybe a new song...)  Good enough for Santana, Dire Straits, good enough for me. Replica of the Orange Squeeze floor box with added controls. While there, check out their other vst plugs.
 
  http://distorqueaudio.com/plugins/vitamin-c.html
 
Melda's MCompressor (free). Allows for precise hand made ADSR envelopes to fit the instrument and environment.
 
https://www.meldaproduction.com/MCompressor
 
Reaper's Reacomp, also free as part of their vst offerings. Definitely have to check out the other vst's in the bundle.
 
http://www.reaper.fm/reaplugs/
 
Can't beat the price and possibly the quality of any of these.
 
John

FabFilter Pro C2 (and Jhudstudio Vocal King)

UAD 1176 the most, UAD LA2A a lot of others, and UAD API 2500 on the mixbus. I also like the UAD Fatso for parallel compression on drums.

I always seem to grab the Waves Rcomp.
trying to break away from that though.
that's sort of why I'm typing this.
maybe I'll try something other than the Rcomp by waves.