I like
Oliver and
Olivia.
Oliver sounds friendly and gentlemanly, and
Olivia is beautiful. If only
Olivia weren't so popular.
Olive is too noun-ish for my liking, but I've seen it used as a first name enough times that it doesn't strike me as odd. I just don't really care for the sound of it, and I'm generally not too big on using "food" names.