First of all, thank you so much, mystery vidder! I am completely excited for anything you do in any of these fandoms!
In general: I am pretty easy to please! The one thing that really matters to me being able to understand lyrics. That doesn't mean don't use a song in a foreign language or something instrumental, but if there are English lyrics I really really hate having to strain to figure them out.
Other than that, I would be happy with a celebrate-the-source ensemble vid for any of these fandoms. I also love vids that do really unexpected or different things with source material. Some more specifics follow (sorry if they're repetitive…I don't remember exactly what I wrote in my request details), but they're just suggestions. And if you hate all of my ideas, I do always enjoy a good ridiculous crack vid!
Community: This definitely lends itself to silly, fun ensemble vids. I also love Abed more than pretty much anyone ever, so an Abed vid would be fantastic! I really adore Abed and Jeff's relationship and certainly don’t mind Abed and Troy, either, although I would prefer them not to be slashed unless it's a total crack vid, in which case, do whatever! In general I'm not too big on pairings for this show.
Little Miss Sunshine: Dwayne is my definite favorite here, followed by Frank, and I love their interactions a lot. Otherwise, again, ensemble is great.
Princess Bride: Fun ensemble gen, action, unbelievable melodrama! I feel like you could do really hilarious and awesome things with this source. Also, Inigo Montoya is the absolute best.
Newsies: My favorite character here is Racetrack and my first ever OTP was Race/Spot, but I'm pretty sure they're unviddable (they're in, what, two scenes together?) Another great fandom for happy or cracky ensemble vids. Also, pair up whoever you like!
RENT: Mark Mark Mark! I love Mark and his sad alone-in-a-crowd-only-one-to-survive vibe, but also his unashamed geeky awesomeness. Everything about him, really. I also love his relationship with Roger, whether you want to do that as slash or friendship. Again, ensemble would be another great choice! Or this, like Newsies, would be a really interesting opportunity for a meta-ish commentary vid (but that's way way out there, just a passing thought if you happen to be excited about that sort of thing).
Slings & Arrows: oh my god, I love this show so much. There's pretty much nothing you could do that I wouldn't adore. I love all the characters. I love all the relationships. I love everything about it. Shakespeary things, ridiculousness and hilarity, Geoffrey Tennant, ghosts, love triangles, character studies…everything about it. I love it all.
Takin' Over The Asylum: I have basically nothing of substance to say about this except, wow, young David Tennant. I am a shameful and shallow fangirl. Campbell! <333