Well, a favourite game we used to play at events was the dye game.
Instructions are simple:
Lay out a field of 5x5 Cloths.
Player 1 gets a normal dye tub coloured blue,
Player 2 gets a normal dye tub coloured red. (different colours are also possible)
When the game starts, the players try to dye a line in their colour.
Very simple, but keeps people occupied when there isn't much going on or you need to prepare something else.
Otherwise.... well, bagball was a big thing, we also had quizzes like that one game (in German "Wer wird Millionaer?") where you get a question asked about Ultima, get four possible answers and have to chose the right one.
We changed the telephone joker against asking a specific player in the audience (you had to name 3 before the game started). The audience joker: Hand out a bag to each person watching with four coloured robes in it - when they chose B for example, they would put on the blue robe.
Only did it with the guild once, because it's hard to invite other players and know they won't just shout in the answers... (thought of trying to make the room "soundproof", and just putting down a communication crystal for the telephone joker)
There are tons of games you can play in Ultima, just takes some imagination.
The death ralley was also something our guild did a couple years ago, and people loved it. Just not sure if it would still work nowadays...
One thing I really loved though was on the Japanese shards - the plays they performed, which showed different things you would usually declare impossible in UO, like playing baseball, falling in a hole and picking apples.
