Quasimodes are sexy, so here’s one for autocompleting HTML5 entity names when you hold down the semicolon key.
This isn’t going to work on a touchscreen keyboard but there are probably better ways to do a quasimode on a multitouch touchscreen.
This is super kludgey and the user interaction doesn’t work quite right, but hopefully it’s good enough to get some idea of the potential for the UI technique.