I want Nicholas' magic mirror. I'd be able to see anyone in the entire world. What fun!
I wouldn't want the I-Ching wands - too unpredictable. You never know what hexagram you're gonna get. The staircase through time is unreliable as well. It disappears, it reappears in another place, it's rarely there when you need it to be.
The disappearing linen closet room could be dangerous. What if it disappears while you're in there? Where do you go? Do you turn into a towel?
The parallel time room is intriguing and probably my second choice, but it's unpredictable and unreliable as well.