i would have to say the trumpet i see it everywhere and even i play it This is someone ele answering the question. Actually a trumpet is a brass instrument it is the most popular brass instrument but you got the wrong kind of instrument. A woodwind instrument is played by a person blows are against a sharp edge or a reed. The most popular woodwind instrument is the piccolo!
The true musical answer is - all of the ones included in a single musical piece - Musicians have argued this for many a long year. But all agree if a piece is written for all the instrument in the orchestra and one fails to play then it is noticeable. therefore every instrument that the composer wrote the piece for is vital.