I have gone to all SK98s and SK68s using Li-ion batteries. Cheap, powerful, and long lasting. SK98s are as powerful if not more powerful than most $100 flashlights and usually run around $10. And the battery lasts longer than the $100 flashlights. They use the
awesome 18650 Li-Ion battery.
SK68s can run on either a single AA or a 14400 Li-Ion, and fits nicely in your pocket. I never go anywhere without one...or two...or three. Seriously, I have so many laying around the house that I can always fine one. They usually run less than $5 each, I buy them by the dozen. Best brand I have found is Ultrafire.