3DConnexion. Flawless OOTB. Integrated quite nicely with all software I've wanted it for (NX and CATIA primarily) and works for misc other applications (internet browser, pdf viewer) that I never required it for, but "it was nice to have" when I discovered it worked.
Comfortable, sturdy, durable, heavy enough to be effectively stationary while in use, quick to get used to (if you haven't used one before)