Because a shotgun shell is really just a shaped charge behind a payload, shotgun shells can be filled with a wide variety of loads, many of which are legal. A California-based company sells many different shells, and has had many different names. Originally known as the Blammo Ammo company, they're currently called Fun Ammo. While most of these shells are legal, they may require an extra hazardous materials charge to ship.
  • Avenger: Hollow steel balls with a low gunpowder load. Short range and low recoil, with low penetration. Could be useful in a situation requiring low penetration, such as home defense. Semi-nonlethal.
  • Bird Bombs: An explosive payload, which (in theory) detonates on impact. Roughly equivalent to an m80 firecracker.
  • Bolo: Two heavy slugs connected by piano wire. Was once known as the garrote slug. While impossible to aim, the wire becomes a very hazardous blade at muzzle velocity.
  • Bouncer: Two zytel (nylon) balls. High muzzle velocity, very low penetration. Semi-nonlethal, like rubber bullets.
  • Chain reaction: A 6-inch length of chain. Impacts in a rather random pattern.
  • Comet: A regular shotgun slug with a red tracer.
  • Detonator: Essentially, a hollow lead slug with an explosive tip. It's made with for the purpose of filling with your own explosive or other payload, which then detonates on impact.
  • Door buster: Tiny lead pellets, approaching lead dust. Impacts with full force, but over a larger area, with very little penetration.
  • Dragon's Breath: Yes, these really do exist, and yes, you can order them for $16.98 each. White phosphorous that ignites upon being shot. Creates a 100-yard flamethrower that burns for about three seconds. Contrary to popular belief, this does not damage a smooth-bore shotgun.
  • Fire siren: A small weighted whistle. Incredibly loud at muzzle velocity. Wear ear protection.
  • Flash bomb: Like the bird bomb, above, but using a flash-powder incendiary instead of an explosive one.
  • Flechette: A whole bunch of needles. High penetration.
  • Hammer: A bean-bag round; a nylon bag filled with tiny shot. High impact, but theoretically nonlethal.
  • Mini Missile: A solid lead slug with a steel core. The lead slug peels away on impact, driving the core through hard targets (like armor.)
  • Napalm: Like the Bird Bomb, above, but filled with white phosphorous, which burns very hot upon impact.
  • Pit Bull: Six big lead pelletes, and one big slug. Not that exotic, really.
  • Shredder: A lot of sharp tacks. Short range, but high trauma to flesh.
  • Smoke bomb: Essentially, the Dragon's Breath Round, only using a smoke powder instead.
  • Stinger: 16 zytel (nylon) balls. Essentially, the rubber bullet for shotguns. Semi-nonlethal.
  • Super flare: A shotgun-launched flare.

While all of these sound like they should be violating a lot of laws, remember that you can just buy your own shell loader and put whatever you want into your cartridges. I suggest that you don't do this, though. I also suggest you don't buy any of this ammo or fire it. Hell, I'm a pacifist, but I'm a geek, too.