Now see, that's just the type of question that I could never answer.
$100 won't buy all the goodies that I want!! But to answer the best I can...
Probably reloading components, or ammo... no, a holster. I need a holster. Well, actually I need a couple holsters. However I'm currently saving cash for a Remington Model 700, so maybe I'd just add it to that cash and go buy one. No, I really ought to buy the shotgun I've been wanting before the rifle. Man I'm going to need a lot of ammo eventually though. Oh.. I can't decide!!
See what I'm talking about.