Adolf Hitler committed suicide together with Eva Braun (whom he had married just two days before) on April 30, 1945, in the Führerbunker (Leader's bunker). He was aged 56. In the testament he left, he circumvented other Nazi leaders and appointed Admiral Karl Dönitz as his successor.

Admiral Karl Dönitz 1891–1980, German admiral. He secretly planned a German submarine fleet in the years following the Treaty of Versailles, was given command of submarine operations by Adolf Hitler in 1935, and replaced Admiral Raeder in 1943 as chief naval commander. On the announcement (May 1, 1945) that Hitler was dead and had designated Donitz his successor, the admiral formed a new cabinet and ordered the unconditional surrender (effective May 7) of Germany to the Allies. His government, at Kiel, was dissolved by the Allies. Donitz was imprisoned (1946–56) for war crimes. (http://www.bartleby.com/65/ge/Germany.html) 4 May, 1945, German forces in the Netherlands, northern Germany and Denmark surrender, Hitler's successor, Grand Admiral Dönitz. . . (http://www.awm.gov.au/atwar/thismonth/index.asp) Grand Admiral Donitz, who had just been appointed Hitler's successor, on 1st May, he spoke of his 'widespread reputation ... (http://www.thirdreich.net/Himmler_by_Fest.html) Though many sources also say that Hermann GOERING was his appointed successor: Commander-in-Chief of the Luftwaffe, President of the Reichstag, Prime Minister of Prussia and, as Hitler's designated successor, the second man in the Third Reich. When Hitler declared that he would remain in the Berlin bunker to the end, Goering, who had already left for Bavaria, misinterpreted this as an abdication and requested that he be allowed to take over at once; he was ignominiously dismissed from all his posts, expelled from the Party and arrested. (http://www.us-israel.org/jsource/Holocaust/goering.html) Goering was designated as Hitler's successor in 1939. (http://www.humanitas-international.org/holocaust/bios_g.htm) The only other person to have such a massive private art collection was the head of the Luftwaffe, Minister of the Interior and Hitler's successor, Hermann Göering. (http://www.crimelibrary.com/gangsters_outlaws/gang/stolen_art/4.html?sect=25) I'm going to go with Admiral Donitz since Goering was expelled from the Nazi Party and arrested just days after Hitler died and Donitz was acting as successor and the order he made for Germany to surrender to the Allies was carried out.