The most unnecessary traffic light I've ever seen is at Main Street and Braun Road in Oregon, WI. Presumably it's for semi trucks turning left from Braun to Main, but even so I think it would function fine with one stop sign.
W. Genesee and Niagara Street in Saginaw, MI. Genesee is a main street while Niagara is not and Niagara generates almost no traffic but the traffic light there functions like Niagara is a busy street. Coming over the river and having to stop there is annoying when there is no traffic using Niagara.
110 at Ashland St., Methuen, MA. Fortunately, it only turns red when there's someone on the cross street (or likely when someone pushes the button, which I haven't seen yet), but it's still unnecessary.
https://www.google.com/maps/@42.7262336,-71.1465533,3a,75y,293.39h,87.17t/data=!3m7!1e1!3m5!1swprMGtF-H5MhPCK-t-KIng!2e0!6shttps:%2F%2Fstreetviewpixels-pa.googleapis.com%2Fv1%2Fthumbnail%3Fpanoid%3DwprMGtF-H5MhPCK-t-KIng%26cb_client%3Dmaps_sv.tactile.gps%26w%3D203%26h%3D100%26yaw%3D16.936455%26pitch%3D0%26thumbfov%3D100!7i16384!8i8192
https://www.aaroads.com/forum/index.php?topic=28871.0