The top 3 most expensive transactions:

• 2015/08/08 15:44:00 - 14.36963 - Creation of the Ethereum Foundation's multisig account
• 2016/06/21 18:18:06 - 13.50000 - WhiteHatDAOContractController operation (throwed exception... ^^)
• 2016/05/28 08:56:25 - 10.70863 - Gatecoin calling TheDAO

A grand total of 8 transactions didn't paid for fees at all:

• 10/02/2016 09:55:01
• 11/02/2016 16:48:00
• 06/03/2016 14:30:25
• 22/08/2016 05:39:53
• 22/08/2016 05:39:53
• 22/08/2016 05:39:53
• 30/08/2016 03:46:30
• 30/08/2016 03:46:30