I haven't seen acoustical paint yet, but it's only a matter of time before some con artist sees the potential in that.
There is, however, acoustical
lacquer. You paint it directly onto your speakers (not the cabinets, the actual drivers). No kidding. And only 300 bucks a bottle - a pittance considering you'll be ruining much more expensive speakers.
Come to think of it, paint does have significant acoustical effect, but only if you're painting concrete. It adds something like 5dB of additional transmission loss to a cement wall. No perceptible effect on drywall, though.