This seems like it could be very useful - I'd modify it myself but since this is frowned upon, I'm making a feature request instead:
The particle object emits particles in a cone, with many settings such as growth over time, fade-out and so on. These are all deterministic, so why not allow it to emit particles in reverse?
That is, it would create particles in front of it and "suck" them in. There are many cool effects that could be achieved with it, as well as some interesting optimizations. I don't see any technical problems with it either.
Now, as I said in the beginning, I'm fully capable of implementing this. Question is, should I do it or wait for Ashley?