It is great grilled, then cut into pieces to put into a taco shell along with some coleslaw.
Or put it in a taco with shredded lettuce, chopped scallion, tomato, and a mixture of plain yogurt (or sour cream) & a little canned chipolte pepper (or salsa of your choice if you don't like it spicy).
Mahi mahi (or any fish) is also good rubbed with a little olive oil & cajun seasoning, then grilled.