Park BBT-29 Double Ended 39,48.5mm 16 Notch External BB Tool
The BBT-29 from Park Tools is a double ended tool that will handle both 48.5mm and 39mm outside diameter bottom bracket cups.
The 39mm end is the right size for XTR BB93 (as well as DuraAce 9000 and some Token BB's) external bottom brackets, while the 48.5mm end is right for FSA Mega Exo and all Wheels Manufacturing bottom brackets. Both ends have 16 notches.
Park Tool quality means this will still be in action in a centuries time.