Re: AR Wrench
There are literally dozens of AR wrenches available.
If you are more specific about what you need to TURN on the AR, I can make recommendations.
I own most of them on the market and have even helped design new ones.
The two barrel nut wrenches that hang on the wall by my workbench (as opposed to all the other more specialized ones that live in a drawer) are both made by DPMS.
They are the gray one for standard barrel nuts and the freefloat one with two replaceable pins.