The St. Louis Market has several. Probably the most unusual is KFNS Wood River, IL. Previous to becoming sports in the early 90s, the station always had a "W" call, most notably WRTH.
Then, later the WRTH calls would end up on 1430 AM, which was originally WIL, but when Bonneville sold them off recently, even though the new owner has studios on the east side, they had to flip to a K call letter and became KZQZ.
KMJM Columbia, IL - the calls used to be on 107.7, before Jacor moved "Majic 108" to 104.9 after acquiring then Christian WCBW-FM. Jacor got the calls on the FM by temporarily parking them on 1600AM, and then they were able to move them over to 104.9 since both stations are in the same market.
Then, you have WIL & WEW the two old timers.
Down to the south, there is KSGM in Chester, IL, which used to be in St. Genevive MO years ago. And KATZ-FM Alton, IL, which was allowed the calls due to its AM sister station at 1600.