Let's say that an uncontrolled airport's ASOS reports wind 060 @ 6 knots. The airport's unicom advisory states that Runway 22 is in use. Am I required to use Runway 22, or can I use Runway 4?
You are not required, but it is advisable if there are other aircraft in the pattern. My home airport often does not have anyone in the pattern and pilots that are based there will sometimes land opposite of the advised runway because their hangars are located at the other end of the runway from the FBO. This means that they can either land long or do a long rollout after landing and then turn off at their hangars. If they landed on the advised runway, they would having to taxi all the way back down from the FBO end of the airport or applying brakes to try to make one of the turnoffs to the taxiway. You just listen on the CTAF and announce your intentions if you don't hear anyone. It is probably more used when a pilot is flying back and wants to just make a long straight in approach while also ending up at his hangar with minimal wait time.
At uncontrolled airports landing is entirely at the pilots discretion, that includes which runway you use. Advisories are just that, the decision is up to you unless a runway is actually closed.
Listen out on the CTAF and listen to what the other pilots are doing, if they are using 4 then use 4 too, if they are all using 22 then there is probably a reason for it.
As the other posters have said, you can use whatever runway you want, within reason. Uncontrolled really means pilot controlled. It is up to the pilot to determine the safest runway to accomplish his/her mission. If the winds are favoring a specific runway, it would be safer to land facing into the wind. If there are aircraft already in the pattern, it would be safer to keep your pattern consistent to theirs. If the mission for your flight is to practice crosswind or tailwind landings (just in case you have an engine out above your particular “impossible turn” altitude), take into account your personal minimums and go for it. Always communicate your intentions to your fellow pilots regardless of the runway you are using. And, an overhead flyover well above Traffic Pattern Altitude beforehand is recommended. Keep an eye out for anyone not communicating on their radios.
As PIC, you are solely responsible for the safe operation of your aircraft. Unicom is an advisory service meant to assist you in that goal, but unlike ATC, you are free to ignore it.
I read about an incident where Unicom advised an inbound pilot that a particular runway was in use based on the last aircraft they'd heard on the radio. However, the winds had since shifted and there was a NORDO plane in the pattern for the opposite runway, which the Unicom operator wasn't aware of because they didn't actually have eyes on the field. I don't recall how it ended (comments welcome), but you can imagine how easily that could turn deadly.