I received three different varieties of fancy schmancy sea salt as a gift; I’ve got ‘Bamboo Jade’, ‘Red Gold’, and ‘Black Lava’ varieties all from Hawaii. The question is, what the hell do I do with it?
One caveat: I’m a mostly-vegetarian, so things like roasts are generally out.
Eat it! 
Seriously, it tastes good and very different than table salt. (Some people will extol the health benefits, but I am uninterested in that aspect and like it mainly for the flavor.)
The Black Lava salt is pretty strong so I would use it sparingly, but if you can’t decide what to use it on, just taste a little bit and see what you think it could improve or what flavors would go well with it or could be enhanced by it. The Red Gold and Bamboo Jade can be used on almost anything (IME) where a finishing salt would be used- I wouldn’t cook or bake with it- but the flavors are again different than table salt and just nice. Try it on something simple like steamed vegetables then go from there depending on your preferences.
Use it on the skins of baked potatoes the next time you make them. If you brush the potatoes with olive oil prior to wrapping them in foil, the salt will stick to them. Yum.
The first I would do would be to taste them individually and find out what kind of flavour profiles they have, and then go to town with experiments. I second the steamed vegetables suggestion, and would add salads, scrambled eggs and sandwiches. I could imagine a hummus and roasted pepper sandwich with a bit of smoked salt.
I made a type of delicious chocolate cookie that called for fleur de sel, but an allowable substitute is sea salt. This one says you can’t substitute, but there are others out there (or just do it anyway - recipe rebel!).
Really fancy margarita?
Knowing me, I’d just eat it. Not all at one go, obviously, but…I’d be tasting it until it was gone, if I liked the flavor.
Also would not be able to resist trying it atop hot chocolate, mmmmyummm…
Throw it on stuff and pretend it’s important. It’s really a blend of minerals and salts, but in reality tasters prefer good ol’ NaCl for most stuff.