I've been trying to make a spinning wheel of blades for a pit booby trap but have been having some trouble. I've got some nice sprites for a rotating wheel with spike bits on it, but I haven't figured out how to make something as simple as an object with animation that stays in place and can have sharpness. I've been trying to do this as an AEmitter - is that not the right approach?

Well, AEmitter emissions don't currently inherit the velocity of the emitter.
They also don't inherit the velocity that a particular point has on a rotating object due to inertia.
So putting a zero velocity emitter on the spikes of your spinning wheel of death just isn't gonna cut it.

You could slap an AEmitter in the middle, and give it a random direction and specific range. This would make a radial damaging effect that would hurt stuff that would touch the blades. I think this is what you're trying to do. But it's not a very accurate model of the blades' movement, and its power isn't dependent on the speed of your spinning blade. In gameplay effect, it would work moderately well, if your blade was always either spinning at a constant rate or still.

But I think I like my way better.
It finds the velocity of a position on a rotating object. With some faults acceptable to this application. This uses some trig functions with angles and crap I don't feel like explaining at midnight, and spawns a particle at that point and velocity. While imperfect, it's a much better representation of a circular saw than an outward radial effect.

I think this would fit perfectly well with your saw thingy, and I'll help you integrate it. But, on some other night, and earlier in it.
At only the cost of credit where it's due.

See, you want to do this the legitimate way. I was trying to cheat.

I have a sprite that is animated to spin. It really shouldn't matter if it's spinning or not, though - the spinning is just for effect. All I really care about is that ♥♥♥♥ gets broken when it hits. ♥♥♥♥ pretty much always breaks when it hits a another object, so I was really frustrated when I couldn't pull it off on purpose.

Simply put, I want to make an object which hangs in the air and hurts when you touch it. The spinning is just for looks.

AEmitter. Emission spread 3.14. Carefully tuned speed and lifetime on the emitted particles.

you could make the blades fake and just hase invisible MOSPixels shooting around shredding everything that falls in.

I'd make it an animated pinned MOSR with a really high sharpness.
Maybe attach a few emitters on the MOSR(that wont move) to ensure damage.
That's the easy, lazy way.

See, I want to do what CrazyMLC is talking about. THAT is what I want. Problem is that AEmitters can't seem to have sharpness. Is that true? Was I just doing it wrong?

If so, I'll just have it emit ♥♥♥♥.

Make it emit stuff and apply

to the particles to make them stop when they hit terrain.

Having the emitters be sharp would be useless, if the MOSR is animating then the MOSR itself wouldn't be rotating. So the emitter wouldn't be moving.