ISO birthday gift ideas for relative/stranger

In this situation, I like to go to World Market and find a big, weird beer. The weirdest one I can find. The gift card is nice, but you can't open and drink it right after receiving it!

Check with the dad whether this is actually a gift-giving occasion. I know it's human nature to try to be extra-kind to this person you're meeting who you hope to be important to you and your family, but I don't feel that a gift is the thing that will cement a good relationship, especially under the circumstances (mixed group of people, camping). Make your first impression with words and gestures, not gifts. If all goes well there will be plenty of other gift-giving opportunities in your shared future. If it were me, I would just bring something for the party; since camping probably not beer/fluids, maybe chocolates, or cookies with a birthday theme. I'm kind of goofy, so I'd consider party goods - a paper happy birthday sign/banner to hang between the trees, or fold-flat birthday crowns/hats, or decorative streamers, something that is cheerful, and a funny thing to have in the woods, but actually not all that complicated to bring.

Stainless steel growler(s)! You can get them at MEC or similar. They would be great for a craft beer lover, as they can be filled and refilled and taken camping. Small ones are $30ish.

Have you asked his father? A lot of giftgivers tend to try to give something novel and unexpected, but the evidence is that https://www.gsb.stanford.edu/insights/give-them-gift-theyre-expecting. Ideally, you'd ask him directly, but it sounds like in this case the closest you'd get it is asking his dad.

Thank you so far for the suggestions - I like the weird beer one. I also thought of bear spray - they've been big news in our mountains this summer and IMO (trail-runner) you can never have enough bear-spray! I appreciate the thoughts behind the "don't get a gift" comments - however, this is a gift-giving occasion - think traditional birthday, just outside. It's not a big deal but it is an "ISO gift ideas" question.

Yeah, consumables hits the right spot. Beer, wine, or booze if he's a drinker, nice spices if he cooks, that kind of thing. Alternatively, can you add a bonus to his dad's gift and have it be from the two of you?

He probably has at least one of everything he needs, and maybe this is me, but I don't think you can ever have too many flashlights, and those are available at all kinds of different price points, with different features and stuff. (Make sure you also include appropriate batteries. Some take weird kinds.) Also things that are described as 'tactical' often make good generic man gifts as well. I got my adult son a 'tactical spork' once and made an absurdly overengineered custom holster for it as a bit of a joke, and it ended up being a huge hit. I mean, don't make something for a stranger, because that would be uncomfortable, but you get the idea. Or if you do the weird beer, maybe add http://www.amazon.com/exec/obidos/ASIN/B001U2RNXE/metafilter-20/ref=nosim/ (lashed to the bottle with paracord, obvs), which are silly and probably superfluous, but cheap and kind of funny.