#2
Its mostly personal preference. The compressors people usually rant and rave about are the original MXR Dyna Comp and the old Ross compressors. Both of those are really rare and carry a hefty price tag. I've seen a few of the script logo Dyna Comps sell for $300 on Ebay. You could buy a boutique compressor, Analogman Bi-Comp for example (which is modeled after the original Ross compressor and the Dan Armstrong Orange Squeezer) but that will also cost you a small fortune for just one pedal.

I have seen a few do-it-yourself sites that have kits to make your own Dyna Comp and Orange Squeezer clones. Maybe you could look into that stuff, if you're handy with a soldering iron.
My Gear:
American Deluxe HSS Strat
Crate GT212
Vintage '66 Fender Champ Amp
Dunlop Crybaby 535Q
Jekyll & Hyde Ultimate Overdrive
Vintage '74 MXR Script Phase 90
Vintage '77 MXR Flanger
Orange Squeezer (clone)
#3
My personal favorite is the EHX Black Finger. Excellent tube compression in pedal form.
Fender Tele > Line 6 Verbzilla > Line 6 DL4 > Line 6 Podxt (With Model Packs and FBV Shortboard) > Yorkville 300-watt Poweramp > Marshall 1960BV