The Light Gun
So-named for the beam of light that this peripheral receives, rather than emits as one might naturally surmise, the light gun brought the notion of projectile accuracy to gameplay. Seen in dozens of games, perhaps the most popular and memorable would be Duck Hunt for the Nintendo Entertainment System. Aside from any notions of improving hand-eye coordination, there's just something visceral about using a light gun to tackle a game's enemies. Though later light guns included a recoil effect, even the earlier models conferred a feeling of power to gameplay that merely coddling a controller could never account for.

The drawback to using a light gun is simply the accumulated muscle strain associated with holding the thing up. It's not so much that the thing is heavy, but even a simple stance held in place over any significant length of time -- say, over the course of completing many levels of a video game -- can cause the muscles to get fatigued. But surely the feeling of freedom and extra capability that the light gun offers is enough to offset that fatigue.

The Dance Mat
Built to play only one type of game, the dance mat is the only peripheral for use with dancing games like Dance Dance Revolution. Consisting of a gridded layout of sensors, the dance mat is meant to be stepped on with some force. But force isn't the main focus of the dance game; precision and speed are. When the symbols start flying at speed, the experienced player never even thinks about where she's stepping; the moves are automatic.

The only problems with dance mats are their specificity. You'd never use one to play Halo, or Civilization, or pretty much any game that requires the use of more than a few commands. But if you're fine with just using yours to dance on, then really, what more could you ask for?