Browsing idly through https://btc.blockr.io/ I found a page with the highest fees paid. There is one transaction with 200 BTC real outputs and a 200 BTC fee, in 2013-Aug-28:

https://btc.blockr.io/tx/info/4ed20e0768124bc67dc684d57941be1482ccdaa45dadb64be12afba8c8554537

It pulled 10 inputs of 20 BTC and one of ~301 BTC (1AUyzod...), paid 20 outputs of 20 BTC and a change-back of ~101 BTC (to 1AUyzod...).

Price was ~120 USD/BTC then, so it was a 24'000 USD tip for the lucky miner. That must have been a mistake by the user, right?

Yes, and Friedcat gave back the transaction fee I believe.

I recall this as well. It was a mistake, the block was mined by Asicminer, and the fee was returned to the owner.