Having glanced through this thread, I feel like most "unpopular opinions" on here are actually just *controversial* opinions, which usually are not all that unpopular. I share a lot of popular opinions, but allow me to contribute what I'm sure are some genuinely unpopular ones, from most to least unpopular.
1. I dislike both standard placements of the Control key. Despite growing up on MS-DOS and Windows machines and scarcely encountering a Mac until late 2004, nearly 15 years into my experience with PCs, I so drastically prefer the Command key shortcuts to Control ones that I swap the left-side Control and Alt on Windows machines, despite spending a majority of my time using Windows again for the past three years.
2. Every linear switch I've ever tried (Cherry MX Black, Red, Speed Silver, complicated green Alps, linear simplified black Alps, linear modded Matias Click, linear modded Alps Cream Damped, Matias quiet linear) I find to be simply horrible. I even game, and have no trouble acknowledging that from a technical standpoint, they're superior for gaming. It doesn't seem to matter how well made or well regarded a switch I try. I just hate the feeling of pressing down on a switch and feeling no tactile bump of any kind. Obviously there are linear switches I have not tried, and I'll never pass up an opportunity to give a new keyboard switch a shot (I feel compelled to try even the cheapest, ugliest rubber dome boards whenever I first encounter them) but man, do I hate pressing the linear switches I *have* tried. It just feels to me like something has gone wrong.
3. I genuinely like Apple butterfly switches. They are, of course, not in the same league as most full-travel mechanicals, but they're my favorite true laptop switch I've yet tried.