Vibranators work well, particularly with the high frequency buzz, they don't do much for the low rpm throbbing, plus when a box shows up at your place with a big bold "VIBRANATOR" printed on the front and your wife goes to pick it up she'll blush
![cheeky](http://ducatimonsterforum.org/Smileys/classic/cheeky.gif)
We have them on the wife's monster and its pretty much completely vibe-free above 5k rpm.
I've also heard of folks having good luck filling the center of the bar up with some sort of silicone, but leaving the straight part of the bar open and then filling that bit about 2/3rds full with shotgun shot, then cap it all off with bar ends. The shotgun shot is free to bounce around and kill vibes - sorta the same idea as a vibranator. No FHE on this method, but the theory sounds like its solid.