From left to right, a standard platinum plug for my car, CR8HIX, R0045J, CM-6, R847, and ME-8. All of them except the first are NGK. All of the interesting NGK plugs are racing plugs and run about $25 each.
The ME-8 has a 1/4-32 thread and is TINY. It is basically the same size as an R/C glow plug. In general, it looks way too fragile and still costs twenty bucks. I'll be trying the R847 next.