Pjur Eros Ultra Glide - the best lube there is in my opinion. Two problems with it: expensive (but a little goes a LONG way, so I justify that - and spit can always be added for additional slick) and it stains some sheets - I just try to be careful when using it.
Gun Oil is a trade name of a lube a lot of people like - it supposedly doesn't stain - I didn't like it but, it's a suggestion.
I like some regular old hand lotion too actually, Vaseline Intensive Care or similar.
Elbow Grease is great too.
Note that the last two are not condom safe.
That's my $0.02.