A light switch with current that has a red and black wire attached but does not control a light or receptacle
You most likely have a split (or formerly split) duplex receptacle somewhere.  

Most of the time, duplex receptacles are set up such that the top and bottom halves function identically and are fed by the same wire.  However, by breaking a small brass tab on the receptacle, it's possible to wire them such that the top and bottom halves function separately.  This can be done to allow one half to be always-hot, and the other half to be controlled by a switch, which I suspect is how your outlet was set up originally.  



Now, if you've checked both halves of all receptacles in the room with the switch and find that they're all always hot, it's time to start pulling off some outlet covers.  If at some point in the past the half-switched outlet was replaced, it's very possible that whoever replaced it just landed all the wires on the same screws as before, but didn't realize they also needed to break off the brass tab.  This would result in the always-hot and the switched-hot wires being paralleled, and both halves of the outlet would be always-hot regardless of switch position.  The fix for this, assuming you want the outlet to be half-switched again, is to shut off the circuit at the breaker panel, and break the tab connecting the two halves.