I’m assuming we’re talking a software compressor?
What platform are you on, what host & what system (64 or 32-bit)?
What have you looked at already?
For example if you have a UAD-2 card there is the awesome “Shadow Hills Mastering Compressor”.
Pretty steep curve on it, but awesome. Uses a combination of Opto & FET type that can be used independently or together for a wide range of possibilities.
There is also the FairChild 670 - the link is for the (in my mind) superior UAD version again but it does have Native emulations from Waves & IK Multimedia
For Native, Slate Digital’s “Virtual Buss Compressors” are also very good, coming in all the usual forms for Mac & PC http://www.slatedigital.com/products/virtual-buss-compressors