Tech 21 Bass Fly Rig. I was using VT BAss DI, but this uniot has the same Preamp, and covers almost all my current effects needs.
I use the v2 of the Fly Rig. One of the things I like about the updated version is that it has two channels for the preamp, so I have a clean channel and a dirty, overdriven channel that I can switch between with my foot.
The chorus effect is nice too and I like having the tuner built in. I wish the compressor was a little less aggressive, it gets farty on me when I turn it up even a little bit. But the preamp section really can't be beat, for the price it's a very nice package of tools in one very compact unit.