Leader Bar is one of my favorite downtown spots for a weekday lunch. It's convenient for folks who work in 200 Public Square and are looking for a casual alternative to the East Fourth restaurants. Service is friendly and usually pretty quick for a sit-down place, which is important during the workday. The food isn't going to blow your mind, but it's good enough and has improved within the last year since their menu was updated. Personal favorites are the Breakfast Sandwich, which is scrambled eggs and bacon in between two pieces of Texas toast served with tater tots, and the Black Bean Burger.
It's a small space and the inside fills up fast, so it's better to arrive earlier during the lunch hour rather than later. During cold weather, you want to try to grab a seat or table near the back because the draft when the doors open can be incredibly cold. The two door system they have going on now is helpful, but not everyone follows the sign to not open the second door until they've closed the first.