Which key do you press for "Press Any Key"?

Actually I prefer the enter key on the keypad. It is easy because it is decently sized and right at the bottom right corner of the keyboard. If you just aim for the corner you’ll hit it.

Spacebar is a backup.

A brief stretch of using Windows 98 years ago “trained” me to never hit “Enter/Return” in “hit any key” scenarios. That was because if Windows 98 (or any other version of Windows, AFAIK; I’m actually a Mac user) popped up a dialog/alert while the screensaver was active, and you sat down at your computer and hit “Enter” to cancel the screensaver, that “Enter” would also “click” the “OK” button on that dialog. So the screensaver would deactivate, and you’d have just enough time to see the dialog disappear but not enough time to read it and find out what you just hit “OK” on.

That said, I can’t even remember the last time I encountered a non-screensaver-related “hit any key” scenario, but I’d probably hit the spacebar.

Well the screensaver is a separate click in modern OSes at least, but I still use Ctrl out of paranoia.

If a dialog box button like OK is given focus, then Spacebar will activate it just like Enter, so that won’t help.

I do that, too, to wake up the monitor (I don’t use a screensaver). Sometimes it backfires on the work machine, and Google desktop search is there waiting for me (double-tap Ctrl) in its modal glory.

Depends. If I know there are going to be much pressing of the Any key in the future or I’m getting impatient, then space bar djembe it is. It the prompt takes me by surprise I’ll often reach for the Esc key instead.

Yup, that came to mind. I thought that was true for Star Wars: The Old Republic after the initial new character movie sequence, but I realized they actually specifically ask you to press the spacebar to continue, and that’s my usual default choice for the “Any” key.