Mobile 1 synthetic wheel bearing grease, but it seperates & runs when the rifle is stored for a while. Works great though.
BelRay saltwater-proof grease is good stuff, thick and sticky, but I'm out...
Tetra-Lube teflon-based grease works well, but is "gun specific" expensive.
Bullshot- bicycle bearing grease, not really hi-temp enough
My current favorite is the free sample I got from Militec-1, mostly because it's a nice little tub that fits handilly in my cleaning kit, but I like the properties of the grease, regardless of the militec properties. The website states the grease is a high quality synthetic grease with the militec oil mixed in. When that's out I'll probably go buy another tub of the BelRay.
Another useful product is a bicycle lube called "Tenacious Oil" made by Phil Wood. This stuff is sticky, but lighter than a grease. It's REAL nice in a straight pull like a Schmidt Ruben (K31)