Designed originally for law enforcement and military use, Pro-Defense calls their F4 Tactical rail-mounted pepper spray the non-lethal alternative. Which I take to mean getting hit by a solid stream of it is still going to hurt worse than the cumulative effect of hammering my thumb, slicing my finger, having my heart broken, eating one too many bean burritos, and stepping on a LEGO. Able to shoot its wad from any angle over 360 degrees, the self defense torpedo comes packaged as The Defender, or sells singly for rail-mounting to personal firearms.
The Defender is a complete kit that includes the F4 Tactical spray unit, plus the "firearm" used to unleash it. A 6-sided rail system and hand grip comprise the latter, and come in 4 different colors. Including pink, ladies. Rounding out the Defender package are a flashlight with strobe, a 2-ounce can of pepper spray, and a 3-ounce can of inert training spray.
Those who buy the F4 Tactical solo will get the device, plus a can of pepper spray, and can mount it on any weapon with a standard Picatinny rail.
The F4 on its own would be my pick. Although the F4 pepper spray stream travels far enough to nail someone up or down a stairwell, I sort of question the value of the Defender. It's big to lug around, and even if included as part of a home defense plan, what are the chances you're going to be able solid-stream a moving target square in the face from even a few feet away during an attack? But putting an F4 Tactical on your own hunting gear could prove to be very handy during an unplanned run-in with a bear or a boar or even a pissed off raccoon. I mean--What's that, Mama? Shoot it? Oh.... Oh. Yeah. I suppose if you're getting attacked by a wild animal and you have a gun you could just shoot it. Huh.
Well I guess if you're not a government official, rail-mounted pepper spray is just for fun then.