For meat? Not Leghorns. Or Plymouth Barred Rocks, unless you have heritage ones.
What are you looking for? Dual-purpose or just meat? There are a lot of available breeds, slow-growing, fast-growing... About the fastest growers you can get are Cornish X, and a popular slow-growing breed is the Freedom Ranger. White Rocks (related to Barred Rocks, but bred focusing on meat rather than on eggs) are something many meat breeds start with, and, of course, Bresse are the "high-end" meat chickens.
Honestly, your options are almost limitless, but it depends what you want. Plymouth Barred Rocks, however, are almost exclusively egg-laying chickens.