Well, in the "nice to have" category would be a set of punches, and a set of bits. I have the Weaver Deluxe Gunsmithing kit, and the Weaver torque driver, finish it off with an armourer's wrench and you'll be set to do everything. A vise and vise blocks can be very handy, especially if you're doing something like removing a delta ring, which I just did last night. This gives you more tools than you could feasibly need to assemble, disassemble, or swap around parts. You don't "need" a vise block, but they make working on the thing a bit more comfortable.
Armorer's wrenches are great and all, but they are very busy. There's too many things going on with them to really get a good grip for breaking factory barrel nuts and whatnot. I had to finangle my two armorer's wrenches together into a makeshift snipe to really get the leverage needed to tighten my flash hider, and even then I just said screw it and left it 90 degrees off since there was no safe way for me to get it the rest of the way.
It really depends on what you plan to do. If you're just separating the upper and lower and dismantling the BCG, you might even be able to do that just using your fingers. I could on my Daniel Defense M4V5, but my new rifle I just finished assembling is a bit stiff and I've just been using a pencil to poke out stubborn bits like the firing pin retaining pin.
If you don't have a vise, you can get them fairly cheap and they do tend to come in handy. You don't need a massive bench either, though one is very handy. Some guys have just bolted the vise to a piece of wood, and then use their body weight on the wood to hold it steady. I slapped together a bench out of project panels from home depot.
There are specialty tools like front sight blocks, intended for supporting the front sight/gas block with guides for pins, but honestly unless you're assembling premium ARs for paying customers you're not going to have much need of it. You'll probably use it twice ever.
Special gunsmithing drivers are kind of handy, if you're dealing with fancy stuff that you don't want to scratch or marr.