I recently had to do this with some earnest

I sold off most my collection due to being in nursing school, had to drop down to one gun!

I kept the AR, 20inch irons, 22lr kit.

I went for the AR for a number of reasons, the 22 kit is a big part of it, I can shoot for cheap, and carry a ton of ammo in either caliber. 20" as I don't plan to clear any houses with it as I am a civilian and that is just asking for it. End of the world a splinter could kill me, right now, well, I'm a civilian, I get to clear one house, and I don't need a 10 barrel to do that well. the other reason for the 20" is it avoids the whole middy/carbine/piston debate, it works, well and its fairly clean and easy on its guts. And I like keeping that little bit of juice. Irons, well, I like irons more, I shoot better with them and they don't break or run out of batteries.

As to reliability, It is a BCM upper on a billet lower with fine internals to match, I have no reliability issues, at all, rain, snow, sand and neglect. I didn't clean this gun for a long time, just to be sure. It works, well and I fully trust it. I've own short AR's, AK's, M1's, SKS's and plenty of others, this gun works better than the rest.