I probably go to McD about 50x per year, but I'm a remote worker, and McD is the only place less than 5 miles away from home where I can go to get decent wifi and human interaction. It's 2 miles each way, so I really like to walk there spring and autumn, have an unsweetened iced tea (a quart for like $1.29), and occasionally a $1 soft serve cone. When I'm really dragging their coffee is absolutely fine, and cheap.
Also, the one near my house happens to be on the east coast greenway, which leads to me meeting a fair number of cyclists heading from ME to FL (or vice versa) stopping in for cheap calories. So that's pretty cool.
It's also full of old people in the morning, and it's interesting listening in on their conversations. There's a set of guys who talk a lot about finance, and there's one in particular whose job, I kid you not, is buying rolls of pennies from the bank, unwrapping them and looking for valuable pennies, and then rolling them back up and cashing them in at the bank. He also owns several apartment buildings in FL, so it seems the pennies are just something to occupy time.
I will never forget how proud he was though the time he found two penny rolls each containing two dimes :)