WordNet (r) 3.0 (2006):

important person
    n 1: a person whose actions and opinions strongly influence the
         course of events [syn: important person, influential
         person, personage]

Moby Thesaurus II by Grady Ward, 1.0:

77 Moby Thesaurus words for "important person":
   Establishment, VIP, baron, big gun, big man, big name, bigwig,
   brass, brass hat, celebrity, chief, constellation, cynosure, dean,
   dignitary, dignity, doyen, doyenne, elder, father, figure,
   folk hero, galaxy, great man, hero, heroine, high priest, idol,
   immortal, interests, kingfish, kingpin, leader, lion,
   lords of creation, luminaries, luminary, magnate, man of mark,
   master, master spirit, mogul, nabob, name, notability, notable,
   panjandrum, person of note, person of renown, personage,
   personality, pillar of society, pleiad, pop hero, popular hero,
   popular idol, power, power elite, principal, public figure,
   ruling circle, sachem, senior, social lion, somebody, something,
   star, superior, superstar, the great, the top, top brass, top dog,
   top people, tycoon, very important person, worthy