+1. Keep it rare on the inside. Just a quick super-high heat sear. Keep the cooking part simple with the seasonings, salt, pepper, garlic, olive oil. Get creative by serving with some sort of sauce on the side, like an asian ginger sesame sauce, or lemon caper butter sauce, or garlic-lime aioli, etc. Or serve with a few sauces so people can choose. You can also grill tuna skewers . Tuna holds up pretty well on skewers, and you are just grilling them for a very short time, keeping it rare in the middle. Don't put anything else on the tuna skewers though, because it won't be on the grill long enough to get cooked. Make your veg skewers separate. You can try some sort of marinade on the skewers like teriyaki. If you go the asian route, you can brush them with sesame oil before grilling.
If you want to try something besides grilling, I like sesame-crusted tuna, which is seared on a hot cast iron skillet (or other skillet if you don't have cast iron). Lots of recipes online for different sauces and sesame crusted tuna.
I'll bet RG has some good ideas.
