If you are after strong compression, you can't go wrong with the 4 knob version Keely compressor. Very good tone, but a bit too "squishy" for me. If you need something more subtle, look for a compressor that has an attack control or can blend in some of the uncompressed signal, like the Barber Tone Press. I find the Tone Press a bit unexciting compared to the Keely, but more suited to my needs. Currently I use a Black Box Oxygen pedal. The controls are effective, but a pain to dial in. I mainly use compression for slide guitar, but occasionally I'll use it for a clean, twangy country guitar solo or squashed power chords. A big part of compression is how much signal you push into the pedal, and some people have trouble finding one that works well with their playing style. Also, higher output pickups, or bass heavy tones will cause compression to happen sooner. I think you just have to try a few compressors to find one that sounds good and works well with your gear and playing style.
Good luck with your search,
Dave