Shimano Premium Grease

Expensive, but this is the best grease* that I have used for loose (ball) bearing hubs, retro caged bearing threaded bottom brackets and caged ball headsets. Not too viscous, coats metal surfaces and reasonably water resistant.
*Nearly comparable to the white lithium Campagnolo grease from the 70s and 80s (dunno if they still make it).

If one is using sealed (marketing lie) bearing assemblies, cheaper grease works just fine.