One that I needed to use a lot in the old days, and still occasionally need: If your font is all messed up, echo C-v C-o. C-v puts you into a literal mode, an

One that I needed to use a lot in the old days, and still occasionally need: If your font is all messed up, echo C-v C-o. C-v puts you into a literal mode, and C-o gets you back into the normal character set. (You probably got there by emitting a C-p at some point.)