Toughest light ever?
My vote goes to the Elzetta ZFL-M60.
I am really picky about having solid lights. I have an HDS, Malkoffs, Elzetta, Fenix, and I have previously owned some Surefire.
Elzetta is the toughest light I have ever seen. And it has a Malkoff light engine with the P60 drop-in capability for upgrading, and it is available with a hi/lo tailcap switch too. Fully Lego-able with other Elzetta parts. They have different heads(crenelated or plain), bodies(2 or 3 cell), tailswitches(twist, hi/lo, strobe), light engines(Malkoff throw or flood).
You can hammer nails with it, while it's turned on, and not even a flicker.
If you look on Ebay, you can find a model(brand new) with the 2-stage(hi/lo) tailcap switch for under $150. If you buy direct from Elzetta, or a full-retail dealer, it will cost more than $150.
Very hard to beat.
Edited to add:
About your AA requirement, the Elzetta is standard with 123 batteries. However, the 3-cell model will also accept a pair of AA batteries too, because they fit in the same length as 3x123. Then, you need to get a light engine which is designed to work on the lower voltage 2xAA batteries, so you go to Malkoff's site and order an M31 drop-in module, and put that in your Elzetta head with the 2xAA batteries in the 3-cell tube, and your light is now a 2AA light instead of a 3x123 light.
Of course that costs more to do, but that's how we get 2AA into the picture
The other thing you can do is go to Battery Junction and get their 3v 14505 lithium primary(AA sized) batteries for $1.50 each. Then you don't have to change the light engine because the pair o 3v 14505 gives you 6v, which will drive the M60 light engine just fine. Another way to skin the cat.
One of the most versatile packages you can find anywhere.
With the HDS, you can get a 2AA battery tube for it too, but it will cost extra, and that will put you over the $150 price you specified also.
If I had to choose, for similar money spent, and similar size(with the HDS having the 2AA tube) I'd choose the Elzetta.
Unfortunately, depending on how you approach this, it's gonna put you over you price specification with either one of these lights, to use 2AA batteries with them. But you can do it.