Loopy Keyboards
I'm such a sucker for absolutely bonkers software keyboards for mobile phones?
I used (and kind of loved) a bunch of different keyboards back in the day, including the super-low-profile Minuum and gesture-powered Fleksy. But one of the wildest (and most interesting) keyboards I tried was 8pen.
Seriously, look at this ridiculous layout:
It's wild, right? Once I figured out how to use it, I got to be pretty fast and accurate at text entry - and it's designed in such a way that (once you learn it) you don't have to look at the keyboard at all.
8pen was (perhaps predictably) abandoned at some point, but I just discovered that there's a refreshed, expanded, and open-source clone of it now:
It's also been enhanced with Vim-inspired editor ability, or something.
I used 8vim to type (some) of this message and it only took forever. I'm sure I will get the hang of this again in no time.