This uses the simple but potentially slow recursive implementation of Fibonacci. Outside a 'short code' contest or a pedagogical setting, nobody in their right minds would code it this way; however it saves:
44b versus first implementation by @mckamey (http://gist.github.com/979716 21b versus "p01's condensation of the same algo (same gist) 21b versus the unnamed version of the same code 11b versus @kassens' very nice variable swapping version (https://gist.github.com/986590)
I'm sure there's probably a couple more bytes to be taken out somewhere!
I don't think you need the explicit
myFn=
part at all (even though you're clearly not counting it towards the 41b)...