Does it mean anything when a guy who you don't know too well always waves at you?

As much as a girl walking up to a guy and saying hi.

If they're being friendly, then no.
If they're summoning up the courage to speak to you, then maybe (depends on the context)
If they're trying very hard to start a conversation and get to know you, then yes.

It's too vague; there's no context; and you're expecting us to answer a generalised question.

It's like asking if bread should be served to everyone in the school; it depends on context.
Some people have a gluten allergy - so no, never; liable to die and prone to a very very serious lawsuit
Some people don't like bread, so no
Some people don't mind bread, so maybe
Some people love bread, so yes.

Context.

Reply 2

Anonymous #2

I assume the wave was him/her acknowledging you and being friendly.