I'd like to create my own shortcut combinations, and it looks to me that the fn key is actually only used for a few shortcuts on OS X. For example, fn-delete is forward delete. In applications like Photoshop it's not used.
Are you aware of any applications that uses fn shortcuts? I don't want to create potential conflicts. If feels strange to think that no software is using such a simple key, and they go for the more complex option-command-shift combinations instead.
Just to be clear, I'm referring to the use of the fn key (eg. the one usually on the lower left side of a MacBook Air's keyboard), not to the function keys (F1 to F19) found at the top of the keyboard.