There's a DC-9 in Italy registered I-SMEL, an Airbus in Egypt SU-GAR, a Nigerian 1-11 5N-UDE.
Didn't BA once have a Britannia G-ANBG that got re-registered prior to being used as a stately hack?
Richard Noble wanted to register his Farnborough F.1 mock-up G-FARN for display at said show, but someone beat him to it having got their cheque in to the CAA a few days before him. Then a friend mentioned to him that he had been saved some embarrassment because FARN is a naughty word in some Scandinavian tongue. So he used G-FBRO instead.
Some wealthy merchant wanted his wife's name (Gail) in his reg, and eventually used various aberrations (I guess GAIL, GAYL, GAEL, etc) until he got to G-GEIL, which, the pilot recounted, means horny, randy, in German.
There's a diminutive aircraft in Switzerland that runs around as HB-SEX. The Italians obviously had no compunction about what got on the register, I-F#CK was an EC39/D Uribel D, I-FEEL, I-GROW, etc.
There's a very smart Cessna 340 based at Mainz-Finthen called D-IRTY...........!
g'night