Personna Gem SE Blades, PTFE Coated
These are the blades you want if you're buying a Gem-style single edge razor, like the ones made by Gem and Ever-Ready. There are a few other variations out there-- uncoated stainless steel, carbon steel, etc.-- but in my experience talking to SE enthusiasts, at least 90% prefer these American-made, PTFE coated blades.
PTFE--essentially the generic name of Teflon-- protects the edge before its first use and the bit that remains contributes to the blade gliding easily over your skin.
These blades are sometimes referred to as "Ted Pellas," after a lab supply company that used to be one of the only sources of them.