For those chippers around in 1993, when the Luxor opened in Las Vegas, their $1 Chipcos revealed a surprise -- a 7 chip series that could only be distinguished with a black light. The chips had UV markings which said:
"Luxor", "Circus Circus" (Luxor's owner), "Pyramid", "Egypt", "Tut", "Nile" plus one that had no UV marks at all. (There were additional error chips too.)

See the MOGH ChipGuide for pics at:
http://chipguide.themogh.org/cg_chip2.php?id=NVLVLU&v=4244169958

That was the most creative use of UV markings, IMO.

It seems that, today, UV markings are not used much, except for occasional maker's marks like the H&C image (various casinos) or the "AI" mark for Abbiati (e.g. Fontainebleau chips). I did see that the $100 Fontainebleau chip also has 2 "bowtie" marks on its $100 (and higher?) chip.

The recent Palms Las Vegas chips, made by Icon, have a UV stamp that repeats "PALMS" in block formation.

I haven't checked locations other than Las Vegas for interesting UV markings. Any recent, or classic, uses of interesting UV's going on that I've missed?