On the "smart" side of the discussion, we do use it to describe intelligent people. It's very very common, but perhaps "clever" is slightly more common.

We do use guy, but only the younger generation does, really. We sometimes use it instead of boy or man, if we don't know which to use. We'll use boy for "he's just a little boy" but where you might use man we might use guy, simly because we're unsure when to use it nowadays.

And on the "funny" side, we definitely do. We might say "that was so funny" or "she's really funny" or "that smells funny" or something. We use it as other countries do.

Just thought i'd add a bit more to the answers