First you can't trade a UNIQUE with other players. Once he'll have it, it will turn to a mushroom when he will leave the current area. You can transfer UNIQUES between your own characters, though. Or you can trade UNIQUES with Daaku in the Elven Caravan, the one(s) you don't want or even all of them after some use, before they "shroom".

Note that with DSO 1.5, it's the only way to have mushrooms, which have very interesting properties...

Here is what Daaku will propose, what it is in reality, and the value of it (if you need money for example, just trade for some wands that you'll sell afterwards).

Some weapons

Magical staff	Two-handed quarter staff +3 (?)	43.500
Fine magical poelarm	Two-handed Gythka +3 (?)
Magical two-handed sword	Two-handed sword +3 (?)	48.750
Magical great axe	Two-handed great axe +3 (?)
Magical staff sling	Staff Sling +3
Magical bow	Bow of accuracy
Magical bow	Bow of accuracy again

Some wands

Magical Missile rod	Rod of Magic Missiles	48.750
Fine Magical Ice wand	Wand of Ice Storms	37.500
Magical Fire rod	Rod of Fireballs	48.750
Magical Stun wand	Wand of Power Word Stun
Fine magical Stun wand	Wand of Power Word Stun

Some protection

Magical shield	Fire Shield (+1, protec/fire)
Magical leather chestplate	Leather +1, protec vs cold
Fine magical leather chestplate	Leather +1, protec vs cold again...
Magical set of bracers	Bracers +4
Fine magical set of bracers	Bracers +2
Magical set of bracers	Bracers +2 again...