Tortious vs. Tortuous:

A slip I caught myself making, though fortunately I caught it in time. A quick Westlaw search suggests others have made the slip, too.

(At some point, of course, each word may acquire the other word's meaning as an alternate meaning, and the Oxford English Dictionary does suggest there's been some element of that for centuries. But the OED still marks this as an error, which leads me to believe that the slippage is rare enough that, descriptively, it isn't yet standard -- and is in any event likely to needlessly annoy many readers.)