WLS -- World's Largest Store (Sears owned it)
WGN -- World's Greatest Newspaper (Chicago Tribune)
I'm not sure if these were given by the FCC or requested. KGO's callsign was requested by GE, the former owner, after the callsign was made available from a deletion of a station in Altadena.
By the way, KFRC was sequentially issued; it does not stand for "Frisco" or "Known For Radiating Cheer". It was issued within the same month as KFRB and KFRD.
KXOA
KXOB
KXOC -- All sister stations in Northern California (KXOA became KIID Radio Disney, KXOB became KJOY, KXOC became KPAY)
These were named after KXO in El Centro. An early owner was trying to create a network out of these stations.
Among the other original and early vanity callsigns in the Bay Area that were issued were:
KKHI (now KKCY) the HI point on the dial
KVSM (now KTCT) the Voice of San Mateo
KSMO (now KYCY) San Mateo
KOFY (now KTCT) along with KUFY (now KSAN) and KAFE (now KISQ) were all coffee-related promotional ideas
KDFC (still KDFC) named for the owners -- one of them was Ed Davis; I don't know the others
KIOI and KIQI represented FM and AM dial positions respectively
KTAB (original sign of KSFO) for Tenth Avenue Baptist church in Berkeley (or was it Oakland?)
KRON (FM is now KOIT, TV is still extant) for SF Chronicle, original owner
KOIT after Coit Tower