It is worthwhile to consider battery compatibility and/or the ability to transfer power across all the electrical gadgets you might be using. My GPSr is powered by two AAA batteries, which inclines me toward a light powered by AAAs, since I could mix and match, if the necessity arises. Power packs and rechargers (Goal Zero Switch 8 and 10 come to mind - I am sure there must be others) are available which can be fitted with accessories so that they can serve as lights, and also recharge one's cell phone, etc. - something that can be rather useful.

Of course one must deal with the profound disadvantage that none of this gear could in any sense be termed "tactical." None of them are even available in camo....