I use all of the keys ;)
The F keys are all used for something, PrintScreen/SysRq are used for screenshots and getting out of a crashed kernel respectively, Scroll lock is for locking the scroll in a VT (or Excel but don't go there), Pause/Break is often used for pausing in games (and is used to get out of a crashed Acorn computer ;))
I've mapped Winkey to compose (anyone who hasn't, I'd do that now and learn how to use it - if you ever need to type in a foreign language or use odd symbols, you won't regret it!)
The rest go without saying...
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