I'm biased of course, but I think Switch Army Knife is excellent. Interesting how I thought about this for a while, but I needed mklotz's "switch" idea as a creative spark. Quick trademark, patent, and Google searches for the phrase "Switch Army Knife" aren't turning up anything of consequence.

Another option is to work off of "pocket knife", perhaps using something that rhymes with "pock", and then adding "-it". Like "Lock-It Knife", because various accessories "lock" into place in the base unit.