To put in context, this is what I bought in 2009 (and some which were subsequently returned or sold): EBS BassIQ, EBS MultiComp, Electro-Harmonix Small Stone, Electro-Harmonix Memory Toy, Diamond Boost-EQ, E-Bow, Keeley C4 Compressor (no longer own), Line 6 Tonecore Echo Park (no longer own).
My favourite purchase was the EBS BassIQ. I never had a Q-pedal before, didn't even have a practical purpose for it when I bought it to be honest, but my cover band added some songs soon after where I needed it (e.g. Fly Away - Lenny Kravitz), and it's just 100% fun to use. I don't have the co-ordination to use a wah pedal, so the auto-Q suits my needs.
The most IMPORTANT purchase though was a Voodoo Labs PPII+ ... by far. Not an effect, but definitely crucial as I was getting ground loops with my previous power supply. I'm now running 9 pedals (including the aux outlet) with virtually no noise.
With all that said, there's still a day and a half left in 2009 and I'm gassing badly for an EHX Stereo Memory Man with Hazarai ... as usual, I'll figure out WHY I need it after I get it.