I know a few, like the Elrond helm gives you elf agility, the rings all shoot a different element, the cake lets you blow up mithril locks, the Balrog helm lets you pull "strong" handles.
But what about the Morgul blade, the 2 headed axe, the grond helm, helm of gemstones, the troll mace?
The Grond helm also lets you pull handles like the Balrog helm.
Sadly I don't know any of the others that you asked about. I wish that I did. I suspect they might only be for appearances, which would be a little disappointing. Considering that many of the basic treasure items are like that however, it wouldn't be a surprise.