One of the classic vocoders was the Roland SVC-350. A quality rackmounted vocoder, still reliable after all these years. For more info on that and other Vintage Roland effects click WVEVIOLATOR
I use the Electrix Warpfactory and love it. I also built A PAIA kit 8 channel vocoder and found it useful for creating some cool effects. You can get these preassembled or as a kit.
check them out: