I don't have a specific favourite room but I love the rooms I staff in (ORAS, Health and Fitness, Challenges, Community Mentoring) Everyone in these rooms are friendly and I'm glad I've made some great friends in these rooms.
Oras is the best. The people have been coming on consistently for a long time, and that combined with the friendliness creates a community where people actually know and understand eachother. Besides that, the rooms topic is pretty generic so everyone can fit in, unlike rooms like doubles where people who never play That don't fit in as well.
Ah, notice how no one is mentioning the Lobby as their favourite. ;] Anyway, as for me, I usually hang in the Trivia, Academics, and Scavengers rooms, and they're all really cool places to hang out, talk, and play games.
The only rooms I really go in are Staff, Lobby, Trivia, Wifi, and THP although I probably spend most of my time in Lobby these days. I actually find it really fun to deal with the chaos that goes on there but at the same time I can have interesting conversations.
I can agree with RP, back when I was around there (as my OC of course). The community is nice (well for some reason it attracts trolls/flamers sometimes) and the RPs are nice, although some RPs get repetitive. :)
As my favorite room is a private one, I won't leak it. But my favorite public rooms are Other Metas, a super nice community with plenty of various cool metas to discuss and play, and also the french room, which is kinda cool.
Ever since I decided to actually be mature and not troll chat rooms with my friends, I've spent less time in rooms and more time watching VGC, so I don't hang out in them much.
But I'd have to say Español, as it's one of the few languages other than English that I can speak. Plus, I have a history of going there whenever I want to battle a friend and such.
Well I was basically a "One-Room-Man" in late 2013, but I sorta expanded it now in 2014, and since I've recently achieved Global Driver, I've made a ton of new friends and the rooms I visit are extremely nice: Recently started visiting The Happy Place because Novae saks, the Tournaments room since I'm auth there and it's a crowded room with quite a good vibe, the Lobby is always funny and plus I'd never miss my chance to ab00se see Sparkychild there, the Help room is lovely, I always enjoy helping users there, makes me feel satisfied knowing someone is happy due to your help.
But what beats them all is my beloved room ORAS (RIP Pokemon X and Y/Pokemon In-Game/Meteor Falls), the room that I basically started out in and has become a joy to many people. An outstanding chat with wonderful people, we have a lot of laughs and a lot of trolls, however, it's always a pleasure. Plus who WOULDN'T want to sit on a chair petting Skitty.