I have two to nominate:

The Luxor Winged Goddess (the original S mm or later G mm version). The overall design is very well balanced with the flowing curvature of the wings, the interesting, delicate hieroglyphics above, and even the unusual rim font as seen on all Luxor strikes. The detail in the wings and hieroglyphics is stunning. As with every Luxor strike I've seen, the design relief is heavily frosted on a mirror-like background -- Luxor must have specifically requested that the dies not be overused in manufacturing to maintain that consistency.

My second nomination would be for the Isleta Casino (Albuquerque) strike. Although I only have their 2001 strike, I think their designs are all the same -- an eagle flying inside a complete ring of feathers. Like the Winged Goddess, this design combines rounded elements that are gracefully flowing throughout the reverse, "violated" by something sharp, in this case punctuated by the sharp wings of the eagle (vs. the hieroglyphics in the Winged Goddess). I'm amazed that this one doesn't seem to command much more than face value at auction, perhaps because the casino only created one basic design, and it's not a NV casino.

If anyone hasn't seen the Isleta strike, let me know and I'll try to scan and post it.