Clannad has several characters that speak normal, formal Japanese (です、ます). I haven't seen any VNs with Keigo, but I'd assume there should be some, in a service industry setting, or business. Even then, some might have quirky characters with slightly weird speech patterns.
If you just want normal, everyday formal speech, Clannad is a good one, since none of the chars who do use it express themselves in strange ways.