You might think about mint. Any kind of mint in my experience will do well in full sun and does not flower. Also this is probably just me but I planted a catnip bed this weekend for my three furry kids. One of my kitties gets so excited when he starts chewing on our one catnip plant that he will flop down on and hug the plant itself. I felt that kind of behavior demanded an entire catnip bed so he can really go crazy.

You know you might look at some of the other herbs out there also. Some (like thyme) don't get terribly tall and flowers are fairly incidental.

Good luck.

Kate