It really depends on what you are looking for, honestly.
If you want a bit more straight forward, guitar solo wizardy filled with some really groovy moments - Population Override. It's like 10 long guitar solos/jam sessions. It's fantastic.
If you want something a bit more...mind-fuck oriented - Bucketheadland 2, Inbred Mountain or Kaleidoscalp
If you want something a tad electronic/beat oriented - Monsters and Robots (well this fits under the next category as well), Bermuda Triangle or Funnel Weaver
If you want some just really cool sounding guitar music with lots of really heavy moments - Albino Slug, The Elephant Man's Alarm Clock, Decoding the Tomb of the Banshee Bot, Island of Lost Minds or Crime Slunk Scene.
If you want something really, really chill and easy to relax to - Colma or Electric Tears.
If you want something like you've never heard - Spinal Clock. It's banjo music. I don't even know if I like this album or not.
And if you want something that samples a lot of Buckethead's different styles - Giant Robot.
Don't even get me started with his side projects like The Deli Creeps or Praxis. And pay no attention to Enter the Chicken. It's really not that good of an album. Aside from 3 songs, its' generally just meh for Buckethead.