I heard that some guy in trademeet will give lots of money for neb's nasty cutter - can't find him. Any ideas

I don't know about a specific guy from Trademeet who will give a ton of money for it but go and talk to all the merchants, see what they give you for it (there aren't that many merchants.)

However, isn't it funny that...

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when you get to Brynnlaw that a merchant there has Neb's Naster Cutter? I sold it to Ribald before I left to go to the asylum so it must have come with me on my ship! Just an interesting note...

The merchant thing is because BioWare uses a trick to save memory in the game: Certain merchants share the same Inventory pool. They were doing this in BG1 as well: Go to BG city and find a General Store. Sell them a unique item or two, like the Wand of Polymorphing. Now go to ANY General Store, and hey wow! they've got a Wand of Polymorphing.