I got this one from a friend and it turned out great. The best part is it only takes 10 minutes to prepare and cook it. I use sashimi grade Ahi Tuna for the steak (whatever size you want), generally they are about an inch thick, between 3/4 pound and a pound I found is best.
All you need to do is get a pan on the stove, turn it on medium heat. Cover the tuna in your favorite oil, not too much, just a decent coating on the outside. Salt and pepper each side, and throw it in the pan. Let it cook for 3 minutes on each side. The sauce for it is as follows: Half and half soy sauce and teriyaki sauce, then as much wasabi as you desire (more for spicier, less for sweeter), personally I like it spicy. Then just pour it over the top right when the tuna comes out of the pan, still hot. Add whatever sides you want, instant rice is simple and keeps cooking time at a minimum, and presto, dinner in 10 minutes. Enjoy.