As far as I know it changes by region; but in latin-america, autobús and ómnibus are the more generic terms used, although ómnibus is thought of as an old fashioned term. Other terms like colectivo, camión (mainly used in mexico), or even bus are used, too. Fun fact - in Brasil, we generally use the variation: ônibus.
Its also called gua-gua in the Canarie Islands. Like Tenerife an Gran Canaria
Why does it have an accent in autobús? In what cases it is used without an accent?