like i said what do you carry in your handle or front grip handle or buttstock for that matter, ill start
front sight tool and an allen wrench to remove my yhm front sight
broken case extractor seems like a good idea.
I’d replace the cotton with petroleum jelly coated cotton balls, sealed of course, and a small fire steel and striker. But that just me.
Dont have anything in mine yet, anyone try one of those handle plug dealies? Saw them today, note sure if they worth it. Dont plan on changing my handle soon.
CB.
Batteries in the pistol grip, spare ear pro in the VFG, tools on the vest for me.
3 rounds, M855.
sail boat fuel in mine;)
I haven’t gotten around to doing it yet, but I plan on cutting off the wrench that comes with Larue mounts so it’s short enough to fit in a Maid grip. It will fit in the 2 extra small holes of the 3 round core plug.
Dust. 
Spare bolt and firing pin in my MOE grip and a front sight adjustment tool and some spare batteries in my UBR when I have the doors on it.
Most inportantly, a small bottle of WeaponShield CLP, but also a BCM SOPMOD extractor kit, some gas rings, firing pin, firing pin retainer, cam key and some assorted allen wrenches. a broken shell extractor might not be a bad idea…
a small vial of machine gunners lube.
Broken shell extractor, derlin pin punch (the push pis are really tight on my carbine), and a front sight tool in the three hole core of my MIAD grip. Small bottle of clp in the UBR. Thinking of getting a RFG for the rail so I have room for a package of Magpul Koolaide. I like the fire tools idea, I think I’ll add that to the kit.