From the most recent event there were a good few items.
I think it was commented that the number of the Tattered Mantles (the cloak) was 5 (
http://vboards.stratics.com/uo-sieg...tifacts-rares-120s-etc-open-until-friday.html ).
I have two of the Crude Orcish Kilts, but do not the figures of how many others dropped. Guessing its similar to the Mantle in numbers tho.
I believe there was a spear to but you'll have to ask one of the thieves about those.
Obviously the Big Majik Flippers were shard wide and not limited to a few.
Older EM items
Can't date these but its some info anyway
Sparkling Green Eggs (EM Cecil). Got them off a Emerald Dragon at Minoc. Not sure how many he spawned at other times of the day, but it was the only one I saw at the time.
A Token of Gratitude from the Yew Guard (Intelligence Bonus 8). Not sure about the details of the event, as I wasn't there but its a very nice item. All were colour changing candelbras and fire spouting, when clicked, but some had stat bonuses which could make a few of them unique. I know one has Strength Bonus and another has no bonus. I'm sure the forum user who has the Strength bonus one might be able to fill in more details.
Thats all the info I have now. But if I find anything else I'll update.