What are some examples of brilliant diplomacy?

This is a very large question since you don't limit my answer to era or even century. Firstly, what diplomacy would count as 'brilliant"? Not just the bringing together of different parties' objectives and finding a means of doing so, but conducting such an interaction with respect and in a positive manner.

Besides the worldwide recognition of great diplomacy in the UK, these are often given as examples: the Alliance Française; the Fulbright programme; the Goethe Institute; the Japan Exchange and Teaching Programme (JET); and the Friedrich-Ebert Stiftung Foundation of Germany.

There are many examples of successful diplomatic efforts so it is hard to choose just one but I would suggest one of the more brilliant examples might be the Egyptian-Israeli Peace Treaty of 1979. While there are still problems between Egypt and Israel today, the peace treaty did put an end to wars that had erupted between the two countries five times between 1948 and 1973.

Both Egyptian President Sadat and Israeli Prime Minister Begin were awarded the 1978 Noble Peace Prize for their efforts. Unfortunately for Sadat, his efforts were not popular with other Arab leaders and he was assassinated by Islamic extremists in 1981.