I really do love the name
Emmanuel, but for me it's one of those names like
Jesus that I haven't been comfortable using though I think it's wonderful. I'm always worried that a child with that name would make the name, or title as it were, less special for me and for people around me who are very religous. :(
David Emmanuel is a really nice combo, I do like it a lot.
David Manuel is also nice, WDYTO that?
As for nicknames I like
Manny, Manly,
Em,
Emmy, El,
Eli,
Elly.