I'm a big fan of chicken souvlaki from Greece/Cyprus.. You can use breast as it is easier to cut into more uniform pieces for even grilling but thighs are more forgiving. For me and the other half I would generally use 2 large breasts or 4 thighs cut into roughly 1 1/2 - 2 inch cubes. Marinate for a few hours with a 1-2 tbsp of olive oil, juice of half a lemon, a couple of crushed garlic cloves, salt & pepper and about a tbsp of oregano.
Thread onto skewers (I find flat edged skewers best as food doesn't slip when turning) and grill direct for 10 minutes or so until required temp reached. I nearly always my GA just for kebabs as the shape is very similar to a Turkish mangal.