I would go with a P60 host of some sort. One light could realistically do any number of things, baring super-extremes.
An 18mm-bored Surefire host of some sort if you want to go gucci (I also just adore Surefire hosts), particularly the C2 for EDC.
Malkoff's MD2-series is another great contender, the 22mm head will allow much more flexibility with different dropins, and they are damn solid. Also able to add all sorts of extenders and things to have more options.
Lumens Factory has their Seraph line, which is the cheapest still mass-sold P60 host.