As most probably know, I am a big fan of single-cell AA flashlights.  I have most of the common versions in my collection and recently added this one.

This Titanium version is a bit spendy but, you can get the aluminum version for a lot less but, I really like it in TI!  Titanium seems to wear better in a blue jeans pocket too.  These lights come in several different emitter flavors as well so, whether High CRI is your thing or you want an SFT-40 powerhouse, they can hook you up.

This is a pretty slim option that fits my hand very well.  As I compared the size to other lights, it is my skinniest AA flashlight and rivals the Sofirn SC21 in size.  The bezel fits inside the bezel of a Sofirn SP10 and the battery tube is even thinner.  It is a little heavier than the ballpoint pen I normally carry but, it doesn't make my T-shirt pocket sag when clipped there.  I also like the UI feature with two head positions for Mode 1 and Mode 2.  In Mode 2, it is super easy to set the default power-on illumination level.

While a bit spendy, I really like this light a lot.  If you want something a bit unusual and very practical, an EAGTAC D3A will serve you well IMHO.