Flag of Germany
When Heinrich XI, Prince Reuss of Greiz was appointed by Joseph II, Holy Roman Emperor to rule the then-new Principality of Reuss-Greiz on 12 May 1778, the flag adopted by the "Fürstentum Reuß-Greiz" was the first-ever appearance of the black-red-gold tricolour in its modern arrangement in any sovereign state within what today comprises Germany – the Reuss elder line that ruled the principality used a flag whose proportions were close to a "nearly square"-shape 4:5 hoist/fly ratio, instead of the modern German flag's 3:5 figure.
List of German flags
Note: Ottfried Neubecker's proposal of 1919 and those of Josef Wirmer in 1944 and of his brother Ernst in 1948 are clearly modeled on the Nordic Cross flags used in all Nordic countries - the flags of Denmark, Norway, Sweden, Finland and Iceland all having the same horizontal cross, though differing in color. 
The flags of the German overseas colonies were first proposed in 1914, but were never implemented due to the breakout of World War I.