My personal favorite is Freso Air Terminal, or FAT.

The city desperately wants the code changed to FYI (or Freso Yosemite International) to market to folks heading to Yosemite that they should fly into Fresno (as opposed to, say, SJC).. and to sound like a bigger deal (International.. even though there's no non-stop international service ).

There are even FYI/Fresno Yosemite International signs all over the airport. But the code remains FAT.