With the transmogrification being introduced in patch 4.3, weapons below could see a spike in interest due to their unique skin. Nothing else matches them in game, and with everyone going back in time and picking up the same gears, items like these will actually start to stand out because there are nothing else like them in game, so if you are looking to be unique and stand out, these are the weapon skin that will do a good job.
Blade of Wizardry
Someone has even started to farm this weapon in TBC dungeon, the average price of this sword on AH is about 20000-60000, it depends on the population of the server you are at.
Teebu's Blazing Longsword
Teebu's Blazing Longsword is an EXTREMELY rare item since the dawn of World of Warcraft. It is one of the first featured epics in the game as it was displayed on the Original WoW packaging. It was held by a Dwarf who was being attacked by a Yeti in Winterspring.
The AH Price listing on WoWhead is moreorless inappropriate. The item really is worth what it is to the person selling it. Some will get rid of it for as low as 2k, others ask as high as 300k (once i saw someone bid it for 200k on illidan-horde). It seems preposterous (that you would pay so much for a 60 BOE Epic) but the item has an incredible amount of history and is usually sought after by Collecters and people who want incredibly unique Transmorg sets.
It is completely unique in design and even though there are few items with similar looking templates Teebu's is in a field of its own in terms of Rarity.
Some other BOP lightsaber
Very Light Sabre(Level 3 quest item, you have to be gnome to get)
Spellfire Longsword (drops 19% of the time off of Mennu the Betrayer)