大巴 - literally a big bus
巴士 - it's exactly the transliteration of the word "bus".
公共汽车 - literally public vehicle, it refers only to buses that are used for public transportation.
公交车 - the same as "公共汽车"
客车 - coach
市区公共汽车 - that's an official name for "downtown public transport bus".
弹头母舱？ never heard of that used to describe a bus. It probably refers to a warhead module of a missile and has nothing to do with a bus.
普巴 - the abbreviation of 普通巴士(normal bus), compared with BRT(Bus Rapid Transit) or special services.
路车 - that would literally mean "road car", but I don't think it's a word.
载客车 - passenger carrier.