The J.Axer's Dapper Topper, Amber's Rad as All Hell Hat and Uncle Sam are unique. There is only one of each, and they were awarded to the first, second and third place winners in the Propaganda Contest.
Some items were gifted in Self-Made quality to their creators. Where an item was credited to a single creator, the Self-Made version of that is the only one in that quality, although this isn't as truly unique as the item is more widely available in normal quality.
Other than the Top Notch, these are the only one-of-a-kind items in TF2.
Other rare items (fewer than 1,000 awarded) include: