Toying with the idea of getting a tattoo. Don't know that I'll actually head in this direction, but I figured I'd get the idea down in InkScape while I was at it.
Public domain, ask if you want the SVG.
I think that's one of the more interesting problems raised with the phipaw! (Wiki has it listed as voiceless labiodental fricative [f], oddly.[1]) I'd heard that phi was chosen as a reference to the golden ratio, symbolizing the balance between anthro- and zoo-morphism, or humanity and nature.[2]
The symbol is hardly perfect, but I think that it does already carry weight for a great many people, so it could be difficult to change if one was looking for something readily identifiable. There's a lot going into the semiotics of the thing.
Link
Irbis
It looks neat, though... phi represents an aspirated 'p' not so much an 'f'. XD (/pʰ/ instead of /f/ if you read IPA)
I've never liked it as a furry symbol as a result.
Is there some way to use, for example, the runic Feoh? (ᚠ)