I use effects a lot, but I don't actually have one I can't live without - I use them as enhancements rather than a basic part of my sound, and I can actually play anything I do without any of them. I generally use them in a very 'textural' way, to emphasise certain parts and changes within a song, and I rarely have more than a couple on at any one time.
My small board, which I use for my 'general' sounds, playing in covers and backup-type bands has:
Dunlop CryBaby 535 (not the Q, the older one with only four settings and a boost)
Frantone Brooklyn Overdrive (actually more of a fuzz-boost than an overdrive really)
Boss DM-2 analog Delay
MXR Micro-Chorus
Boss PH-1R Phaser
My large board, which I use for my originals band and for a lot more specific sounds has:
ZVex Fuzz Factory
Dunlop CryBaby 535
DOD FX25 Envelope Filter (the older 2-knob version)
Boss OC-2 Octaver
Frantone Cream Puff fuzz-distortion
Boss DF-2 Distortion-Feedbacker
(then an insert point to go into the amp's preamp)
MXR Micro-Chorus
Boss DM-2
Boss PH-1R Phaser
Boss HF-2 Hi Band Flanger
Roger Mayer Voodoo Vibe with speed control pedal
(that lot in the amp's FX loop)
Sometimes: Vermona DAF-1 Dual Analog Filter (a rack unit that I rarely use now because it's my only remaining one, and it's a pain to carry a rack just for that); ZVex SeekWah (a truly brilliant box but very difficult to use live if you need to change settings)
Both these boards rely on using the amp (a Mesa Trem-o-verb, although other things work OK too) for my main overdrive sound, but if I don't have that I use a Mesa V-Twin pedal.
And failing all that, my 'one pedal in a pocket' impromptu jam or emergency-backup-if-everything-else-goes-down pedal is a spare Boss DF-2... so you might say that's my 'favorite', possibly. But not the one I use most normally.
For bass I also use pedals

.
Frantone The Sweet distortion-fuzz
Frantone Lo-Tone Classic Fuzz (more of a fuzzy overdrive really)
Frantone Thunderhead bass booster
Boss CEB-3 Bass Chrous
Dunlop CryBaby 105Q
(+ space on board probably going to be filled by a bass synth pedal of some sort)
All boards also have a Boss TU-2 Tuner on.
Come to think of it I also have a Frantone Acoust-a-Boost which I use on my acoustic too...
