This is a uniquely suitable mic for harp or beatbox.
First of all, the size makes it comfortable and practical to hold in the hands.
Harp & beatbox are both unusual in that the audience can't really see what you're doing. So it helps that at least this is one lovely looking mic.
Hand wah effects are easily possible, although not as pronounced as for acoustic harmonica nor for green bullet style Chicago blues. I reckon this is due to the pronounced cardioid sensitivity pattern. On the other hand, this also makes the Fireball-V as feedback resistant as you're likely to get, especially if playing through an amp (for which you'll need an impedance converter). Perhaps it also cuts down on handling noise; in any case, handling noise is very low.
The integral volume knob is indispensable for both shaping your tone and for keeping feedback at bay, harping through an amp. It operates silently and is ergonomically accessible.
The integral pop filter is pretty effective, helping to cut down on breath noise through the harp. It also makes it better than say an SM57 for close mic'ing of vocals.
The clip is of better quality than you'll find supplied with most dynamic mics, even though it's primarily designed to be hand-held.
Audix themselves give a low-medium rating for proximity effect but it has substantially less than say an SM57.
Tone-wise, you get a nice bluesy fuzz that's grittier than an SM57 without being so saturatedly overdriven or honky as the Chicago blues sound. In terms of frequency response, the Fireball-V is a little peakier in the higher range than a '57. It also has a very gentle lift in the lower musical register, as you'd want for harp.
Being dynamic, the output isn't super hot, but it does seem to be more attentive to finely detailed nuances than you'd expect.
There is nothing else out there that compares.