This is Sterling, posting here with the new pup because ... well, because he's the one who's logged in and I'm too lazy to change. So there.
Surprisingly I pretty much agree with Jack across the board, but I'm not surprised by this because he's a pretty smart guy.
Zombies: Most of my pups would be all: "Oh, this again? *yaaaawn*" but some of them (like this one) wouldn't quite know what to do and it might lead to some breaky.
FlashForward: Ditto Jack, especially re: "Who can I shank for it?"
Aliens: I could see it working if it was a sort of Mars Attacks! scenario, where suddenly we're overrun by aliens like none that we've ever seen before and who are hell-bent on blowing everything up (or IDK, making sure everyone has a new puppy and an espresso macheen, wtf do I know about aliens and their motives?)
Space!: Could work with a bit of structure, ie: crew, passengers, janitorial staff, are we on a ship or a space station? Is there a replicator? Malfunctioning holodeck? Borg attack every Tuesday?
Random: Is always fun, and I do like the idea of alternating batches of crazy instead of all at once.
Other!: I do like the What If idea, especially since I was moving and had no 'net access the last time the Alternaverse plot rolled around. Genderswap plot is generally made of win. Bodyswap plot could be as well.