The 3-pin variety...
. Also don't be tempted by dremel wanna be's as most of them are a pile of junk (if you do just make sure it has as good as or better specs than a dremel and ull be fine). Oh yea and get urself some goggles i don't use them (need to get a pair) and it's an extreme pain in the arse have to squint my eyes to stop anything flying into my eyes (and trust me it will try to
).