[Saurreg]

I think almost all the minor characters with some form of importance or another have been listed. But if we are to expand the scope of this thread to include other characters in the expanded LoTR universe, I would say King Brand and Dain ironfoot are two minor characters that played important roles in the War of The Ring. Without their staunch defence of Dale/Erebor, the armies of Sauron could have entered Eriador and caused untold mayhem and destruction. Gandalf said that there could have been "no queen of Gondor", that must have meant that even Rivendell would be threatened.

Dain standing over the body of Brand, defending it from enemy hands until he himself expires, whatta dwarf...