Sometimes, people have life problems that can be entirely solved by doing one thing. (doing X made my life 0.1% better, PERMANENTLY!) These are not things like "This TAP made me exercise more frequently", but rather like "moving my scale into my doorway made me weigh myself more, causing me to exercise more frequently" - a one-shot solution that makes a reasonable amount of progress in solving a problem.
I've found that I've had a couple of life problems that I couldn't solve because I didn't know what the solution was, not because it was hard to solve - once I thought of the solution, implementation was not that difficult. I'm looking to collect various one-shot solutions to problems to expand my solution space, as well as potentially find solutions to problems that I didn't realize I had.
Please only put one problem-solution pair per answer.
On a similar note, I use a kinesis advantage; I had to choose between that and an ergodox and expected to like it slightly more, but I can't actually compare.
I've set it up so that if I hold caps lock, I can control the mouse with my right hand. Not as fluidly as I'd like, at least partly due to (what I believe to be) bugs in the xkb code implementing such things. I can only move 100px at a time. But I also have focus-follows-mouse, and that makes it really easy to jump between two windows, which by itself is a decently big win.
caps lock also mirrors the right side of the keyboard to the left, letting me type (slowly) with one hand and mouse with the other. I haven't ended up using that much though.