The only one tool of this kind that really lasts is a Foredom and its only availabe corded and its expensive. It uses a flex shaft and a tool holder so its a little less convienent to use. Plenty of torque, power and rpm for whatever. I bought one to use one as in gunsmithing - does all teh stock work to get ready for bedding actions and all polishing chores. Use it for heavy duty rc chores. Been using mine for over 20yrs.

Drawback - its expensive and the flex cable need routine maintenance.

http://www.gravescompany.com/foredom.htm