Oh wow. I just realized that Monks are proficient with any weapon with the monk quality. That opens up the Seven-Branched Sword, the Rope Dart, etc etc etc. There are bunch of good options with that on the table.
As for unarmed vs weapon. It depends a bit on level, but weapon is going to win out early on and unarmed is going to win out later. Regardless of build, you should be using a weapon almost exclusively for levels 1-3.
However, Unarmed is the only thing that works with Style Strikes, Stunning Fist (and derivatives), Vicious Stomp, Enhanced Ki Throw, Bleeding Attack, Enforcer, the extra attack from spending a point of Ki, etc. Unarmed also has the advantage of allowing you to perform grapples. I think it may be useful to list all of the things that only work with unarmed attacks before really assessing a focus.
I keep wanting a Greater Trip + Enhanced Ki Throw + Vicious Stomp build to be effective.
An aside, if you are playing exclusively at very low levels (like 1-4) or if you can retrain feats then Bleeding Attack is amazing. 1d4 damage at that point is "they are dead and just don't know it yet" for a lot of things.