Excellent! I liked the stethescope one and the table one.
Here's a few I thought of:
If there is just yourself and one other in the lift, stand that little bit
too close to them.
When a person gets in and presses for a certain floor, tell them, "I wouldn't go there mrs/mr!" sounding serious, shaking your head and huffing through your teeth.
When you're in the lift by yourself, get totally naked and just stand there calmly when someone gets in, nod and say, "Alright mate."
Or start to get to changed and say, "I'm late for work."
Get into the lift, with dark glasses and a white stick. Fumble for the floor you want, ask for help, saying you can't see and then proceed to get the paper out and start to read it.
When it's completley silent, say to someone, "This one's always getting stuck."
You can always add to the above, "In fact, I had the fire brigade out last week. Stuck in 3 hours I was. They had to PULL me out."
Get in the lift and press every button, then say, "Can't quite decide which floor I fancy."
You can always get a friend in on it. Start discussing the variable highly infectious diseases you have, then sneeze.
There is always the classic fart. You can add, "Oooo, now that
was a ripe one!"