How about a Holly? We have a beautiful Holly hedge which easily gets to over 6 ft. if it isn't pruned back. I am in zone 9 but I think Holly should do ok in zone 7. Our hedge is probably 30 years old and is joined on one side with a Prycanthia hedge of equal age. The Prycanthia used to be almost trees until the neighbor asked if they could "trim it a bit" Next thing it was around 3 ft. instead of around 8 ft. and nearly dead (thier intention I'm sure, they don't like our hedge)
The Holly will put out suckers though. We just mow over them.
Shell