Danik
Yeah, Ctrl/Cmd and Shift are already used with the fill tool, and Alt is used for color picking, but I'll think about it, thanks.
Contiguous/Global Shortcut
Ryuza
Not sure if this has come up as a suggestion before but I was wondering about a shortcut to switch modes for the fill bucket/magic wand. In Paint.NET when you're using either of those tools you can hold shift to toggle contiguous/global.
It's really handy as it lets you keep contiguous on or off as you prefer and then easily use the opposite setting whenever you need it without having the manually switch back and forth.
I'm not sure what the shortcut might be though since shift is already in use for both tools.