Bearing grease for loose ball hubs and bottom brackets. Pretty much any wheel bearing grease you can find at your local auto parts store is going to be more than good enough since the loads on bike bearings are minuscule compared to the automotive applications those greases were engineered for.

Some people prefer (boat trailer) marine grease since it should be a bit more impervious to water intrusion from riding in bad weather. I've been using Lubrimatic 11404 marine grease myself and I'm happy with it, but any brand should do.

You'll only need to grease bearings if you've got loose balls, though. A lot of modern bicycles use cartridge bearings for bottom brackets and hubs, which aren't intended to be serviceable. Use 'em until they wear out, then replace the cartridge.