Birthday Gifts for 18 Year Old Boyfriend

My Dad's a hunter & fisherman, got him an LLBean leatherman a few years ago, he keeps it on him all the time. Its several tools in one. Get one in the mid price range $30.
Or get a journal to keep track of what he catches...

Can you crochet or knit? If not, is there someone who can teach you? A warm, handmade scarf or afghan made with camo colored yarn makes a nice "manly" gift for a sportsman of any age.

It isn't that great a gift but get him a gift certificate to his favorite hunting/fishing store.. Without knowing what he already has I can't recommend a particular fishing pole or anything like that. If you know what store he frequents for his supplies you can go in and ask them. They may remember him talking about something he would like to have. Or recommend something they know he doesn't have but may enjoy. This will be particularly true if it is a small shop (owner operated) or has been there a good amount of time with the same staff.