I really used the Enter key on the numpad a lot because it's easy to find, bottom right corner.
I still miss Apple's distinct return (start a new line) and enter (submit dialog box) keys.
I also occasionally use Alt-Codes for special characters like the Trademark ™ or the occasional ☺
Windows extended character entry became an obvious joke for me once I got a Mac and realised that you could enter all sorts of characters straight from trivial and easily memorisable key combos. In Windows I get most o these I get from John Sullivan's
United Kingdom International keyboard layout (not much use unless you're British), but the rest (including obvious omissions like em and en dash that he won't add) I make up with
Autohotkey_L. The Unicode builds of Autohotkey provide reliable Unicode entry such as
^!N::SendInput {U+2192}
to make crtl-alt-N give "→". I've moved UK Int’l’s ™ to ctrl-alt-shift-M, to allow ctrl-alt-M to give −, a real minus sign, alongside ctrl-alt-Z ÷ and ctrl-alt-X ×. There truly is no excuse in the 21st century from still being limited to the symbols that they could fit onto a typewriter.
Alt-nnnn is for chumps. I don't like Mac OS X, but at least it provides a more palatable way to feed people Apple's superior thought processes than Mac OS 9, which pretty much anyone technical wrote off without ever spending enough time with to truly understand and appreciate. That includes native support across the board for extended character entry, that I'm simply copying in Windows (including some of the same key combos).
TL;DR:
Don't waste time using alt-nnnn codes, you idiots!
Also, Topre == buy if you can afford (true of any switch type though)