I think the most popular is using a wire wheel on an angle grinder
Though if I want to preserve paint or very fine markings, I'll use evaporust - or if I have some very fine rust and don't want something as aggressive as the wire wheel - a quick hour or two in evaporust can be just the ticket.
an alternative for light rust can be WD40 and steel wool.
with heavy rust, the wire wheel will leave a "patina" which is actually still rust, but can still look pretty good. if I wire wheel and then rub down with some mineral oil, it will turn kind of dark and look clean but still old. evaporust (or vinegar) will remove ALL of the rust and can leave the head kind of dry and pitted looking - but note that some people think the chemical is pitting the steel - it is not - the rust pits the steel but the chemical removes the rust from the pits, leaving the pits - whereas the wire wheel can kind of fill in the pits with rust or whatever and it won't look quite as pitted sometimes (depending on the nature of the rust and pits).
evaporust (or vinegar) can be handy though on letting you know exactly how much high carbon steel is left in a bit though on a worn axe. You could soak in evaporust, and then wire wheel - or soak in water and let re rust and then wire wheel if you want to get the patina'd look.
