People seem to like food favors the best so they aren't stuck with something sitting around for a long time. You could do small packages of cookies or macarons, a DIY candy bar where guests fill up a bag, or M&Ms in your wedding colors. Tea or coffee is also nice. For a non food option, a small herb plant or succulent with a cute tag attached (I think this is what I'm leaning towards). I think it's really nice to fit a favor into your theme/season/colors if possible, and you can check out a lot of ideas on pinterest.
I've seen mints and chocolate. However I would think about not having favors. Most guests forget them or never eat them as well. We decided not to have any bur instead people can take our decorations like mason jar centerpieces or some frames. We are having 90 people so also consider the size of yours too. If its more intimate like under 50 then try and provide something.