Fajitas are dead easy in a GF grill - just chuck on your strips of steak or chicken with some peppers, onions and a packet mix (such as Old El Paso). While it cooks get some salad ready and eat it all piled into soft tortillas with salsa, mayo, sweetcorn or whatever you fancy.
I also do paninis and toasted sandwiches on them.
I just got one at Christmas and ABers recommended trying to do fruit on it too (apple with cinnamon, banana etc) to go with icecream. Haven't tried it yet... but will do...