Exhibit 2.1 AMENDMENT NO. 1 TO AGREEMENT AND PLAN OF MERGER THIS AMENDMENT NO. 1 TO AGREEMENT AND PLAN OF MERGER (this "Amendment") dated as of April 18, 2006, by and among Pinnacle Entertainment, Inc., a Delaware corporation ("Pinnacle"), PNK...Agreement and Plan of Merger • April 19th, 2006 • Aztar Corp • Services-miscellaneous amusement & recreation
