If you're talking about Windows apps that keep me from switching to Linux, I have an oddball one: it's a keyboard re-mapper that I wrote back in Windows 3.1 and still use. It does the same re-mapping in
every application (except for some reason in Microsoft Edge). It's not a simple 1-for-1 mapper, which I think is readily available in Linux.
At the simplest level, it re-maps ^H to the left cursor arrow, ^N to PageDown, etc.
But it gets more complicated: ^D maps to seven down cursor arrows (i.e. it moves the cursor down seven lines), ^U in the opposite direction. ^C usually (more details below) maps to ^Left (i.e. go to the beginning of the word), Shift-^Right (select to end of word), and ^C (copy selected text). (Notice the final ^C does not cause recursion!)
^A once goes to the beginning of the line, ^A twice goes to top of screen (I forget the exact keystrokes it emits, but this works with most apps), and ^A thrice goes to the beginning of the file. Analogously for ^E, but end.
Finally, it has two modes. In the normal mode, all the cursor control keys do their normal cursor movement thing. But type ^Q, and the cursor keys are now in select mode: ^H outputs Shift-Left, i.e. selects the character to the left, etc. Drop out of select mode with ^C (copy selection--different from what I described above!), ^X (cut selection), or ^Q again (do nothing with the selection).
I'd love to be able to reproduce this kind of behavior in Linux. I'm sure it's possible, but I don't know enough about keyboard re-mapping, or keyboard drivers, to do it.