I do a lot a remapping...

I'm using .Xmodmap under Linux and KeyRemap4MacBook under MacOS to remap these:
PrtScr -> Mute
ScrLock -> Vol-
Pause -> Vol+
As I use a PC keyboard and often switch between Linux and a Mac, under MacOS I remap the modifiers keys to act exactly like on a PC. So Ctrl will act as Command and Win acts as Ctrl. The navigation key are remapped when needed to emulate the behavior of a PC. For example PgUp shows the previous page AND moves the cursor, instead of showing the previous page but leaving the cursor in place (which is the default behavior on a Mac and I hate it).
Then, because I'm an AZERTY user and also a programmer, I remap some symbols that are very awkward to type on AZERTY:
[ I get with the key at the left of 1 (on AZERTY it does superscript 2 which I never use)
] I get with Shift and the key at the left of 1 (it does superscript n on AZERTY, never used it)
{ I get with AltGr and the key immediately above
} I get with AltGr and the key immediately above and at the right
| I get with AltGr L
\ I get with AltGr and the key immediately at the right of L
# I get with Shift and the key immediately to the left of the right Shift (on AZERTY it does the paragraph symbol which I never use)
I'm seriously considering switching to QWERTY keyboards just because typing programs is so much easier on them. I know I can do it as I learned to type on QWERTY anyway (on a TRS-80, more than 30 years ago).
Now that I have a programmable keyboard (KBT Pure Pro), I do all this remapping in the keyboard itself. I have even added a key which does this:
[ ] Left-arrow
So it types the brackets and moves the cursor back between them. Very convenient for C, Objective-C and many other programming languages.
Oh and one last thing. On the KBT Pure Pro, the right Ctrl and Shift are not very useable because they are small and packed with the arrow keys. So I remap Shift to Home and Ctrl to End and it's very convenient. I have found it quite easy to adapt and use only the left Ctrl and left Shift as modifiers. I don't miss them much on the right.