A Magnanimous Benefactor is a one time only quest found at the top of the Sun's Reach Harbor inn that can only be acquired at Exalted reputation. If A Charitable Donation was a money sink, A Magnanimous Benefactor is a money black hole. The reward is very, very cool, though. For the low, low price(donation!) of 1,000 gold, you will be awarded a title, 'of the Shattered Sun.' For example, I would become Alex of the Shattered Sun. Sweet.
Now, a thousand gold is a steep price, but in my opinion this is one of the cooler titles in the game. My main has Hand of A'dal, but Of the Shattered Sun sounds way, way cooler, even if Hand of A'dal has more prestige. This title is also unique in that you can acquire it purely through solo play. Justicar/Conqueror can be gotten through semi-solo play, but you need to join groups and raids in Battlegrounds. Plus, it takes way longer to get.
If you're Exalted with the Shattered Sun Offensive, you probably have far more than 1,000 gold. All of those daily quests(and/or Magisters' Terrace runs) up to Exalted? Go ahead, spend 1,000 gold. Have something to show for that work.