As you're by this point well aware, Valve is less a singular, unified company and more a series of creative cliques - with all the disjointedness and occasional infighting that entails. On the upside, that allows for all sorts of zany, deity-defying experiments, up to and including controllers tailor-made for that lumpy thing protruding from the bottom of your back. Also, your tongue. Thankfully, the two are not being used in conjunction. Go below for videos of Valve engineer Ben Krasnow's two extremely, er, unique controllers.
Obviously, the controllers are very, very early prototypes that may never amount to anything substantial. The implications, however, are actually quite fascinating. Neither control method is ideal, but the sky's the limit for people with disabilities or when other control options are physically unfeasible.
It's admirable work, not to mention technically impressive to this writer's flabby, mechanically hopeless mind. Also, come on: who hasn't wanted to have perfect 1:1 control over a Left 4 Dead smoker zombie's tongue? And if Half-Life 3 doesn't include a tense sit-down dinner negotiation scene between Gordon Freeman and the G-Man controlled only via tongue and backside, then that's it. I'm out.