I have either shooting slings or tac slings on my rifle. Depending on what it is. For my main field rifle I carry it a lot more than I shoot it, so I have Blackhawk tac sling on it. It helps to carry it for long periods of time, and it is nice to be able to drop it and use both hands. (This is with a 10 lbs. FAL, which can get a bit heavy after 30 miles of rocky shale in a weekend).
Other than that, I do not have a muzzle brake on any of my guns. Just crowned muzzles. No flash suppresors, I just try various ammo at night until I find one that I like.
Some rifles are scoped. Nothing fancy, though I plan on purchasing an ACOG later this year. (tried a 3X chevron rectical compact model, fell in love).
No bipods.
Lots of mags.
First and most important purchase, a couple cases of practice ammo.
I could see how a light mount could come in handy, but I currently do not own one.