Hey, someone was going to do it right?
I'll start with a few of my favorites. TDR Kotelnikov, TDR Feedback I and II, TB Bus Compressor, DC8C2, T-Racks Bus Comp, Precision Comp, Opto Comp,  Fab Filter Pro-C, and the Pro Channel Bus Comp.
I probably use the Pro Channel bus comp and Kotelnikov the most, but I like everyone of these compressors a lot.

I also use MSpectralDynamics a lot, but keep in mind that if you use the 64 bit multiband that ships with Sonar and turn the threshold down and the ration down, it works kinda sorta similarly. I guess it's a poor man's version.

 I'm too stupid for MSpectralDynamics.

I prefer to use the Manley Variable Mu emulation on the Focusrite Liquid Mix on all my songs.

Pro-Channel Bus Comp and Virtual Bus Compressors are my main go-to compressors for mastering.

clintmartin
 I'm too stupid for MSpectralDynamics.

That's actually why I like it. After following Bitflipper's guide I can make use of it. I don't have the training, skill, or any of that to actually make any intelligent choices with a multi-band compressor. However with MSpectralDynamics all I do is drop it on the master bus and basically play with the wet/dry setting, and maybe the slope. I'm sure I could get better results if I knew what I was doing, but doing that very often gives nice results. It often needs no tweaking to improve the sound.
 
And if I find it doesn't, I just leave it off.

My chain usually starts with Waves S1 if balance is off. Then I will use a Flux Alchemist multi-band compressor. The beauty of this one is that it allows you to Expand one band, while compressing another. I can typically punch up a kick or snare, but smooth out guitars. The Waves Linear-Phase Multi-band compressor is great, as is the C6. Other compressors I use for loudness or otherwise just power, are the Waves API-2500 or PuigChild 670. I've used the Waves SSL Compressor, but I find it too limiting (no pun intended). It doesn't always provide excellent results in a master for me. However, these can all add both glue and punch, if used with care. 
 
DMG Audio's Compassion is quite great but I haven't spent enough time with it in Mastering yet. It's feature-rich and flexible.  
 
If the kick is too punchy and the bass is buried, I will use the Sonalkis CQ1 dynamic compressor. If you've listened to Rush's Roll The Bones album, you can easily tell the kick drum is just to up front and punchy. That 18" kick was just wrong for that album, IMO. So, I ran that '97 re-master through the CQ1 and balances the bass vs. kick better. Now, I can listen and enjoy the Wal bass more. Same with Presto. 
 
Depending on the recording, I might even add the Waves J37 or Kramer Tape to gain another 3db of loudness. 
 
Lastly, I typically use the Waves L3-16 for limiting. 

I haven't purchased the FabFilter compressor yet, but it is on my shopping list, as is the multi-band version.
 
I've downloaded TDR Kotelnikov but have yet to try it out.

I just picked up SKNote SDC- Stereo Double compressor. It is a copy of the best hardware out there the shadow hills comp.  It has tons of knobs but you just dial til you get a great sound! Presets for it would be nice but, I am having tons of fun dialing it in.