A model that kind of intrigues me, but I cannot quite convince myself to get it, is the Rovyvon "Angel Eyes" series, that combines an on-board Li-Ion battery with a replaceable AAA, like so:
Discover the Angel Eyes E3 Plus dual battery keychain flashlight - your perfect EDC companion! With a maximum output of 700 lumens or 90 CRI, this powerful flashlight is perfect for any situation. Get yours today!
www.rovyvon.com
On the one hand, cool concept: I like the combo of easy USBC rechargeabilty with easy use of regular AAAs if that's what you can scrounge. But the package looks bulky, and in particular it looks bulkier than a decent AAA light and a decent small rechargeable (such as the A5 shown above). Having both lights unitized might be better for keeping them together, but it makes a bulkier object as a whole.
Also: not cheap!
Anybody have experience with them?