I did a few in my life, and usually in F or J class or a combination of both.

I did one with my partner to celebrate New Year 2000 and the itinerary was
CDG-SIN-PER-MEL-SYD-AKL-EZE-IGU-RIO-MIA-CDG on Oneworld in J and F
We celebrated New Years eve in Sydney with a splash

The most memorable RTW was the one I did in October 1993 on the Concorde
It was an Air France aircraft specially chartered for the trip.
It was an amazing experience since the aircraft visited places it had never flown before and attracted thousands of people to the airport to have a glimpse at it.
The plane was like our motorcoach, we could leave some personal items on board between flights and so on. the crew was the same for the 18 days trip.
The itinerary was : CDG-IAD-LAS-SFO (refueling stop only) HNL-PPT-NOU (refueling stop) SYD-DPS-CMB-MCT-CAI-CDG

A lifetime experience!