^Oh yeah. Toy Story had some of the most hilarious trailers, I’d say. I couldn’t stop laughing after the first time I watched some of them. 
Here are my top 3:
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The Incredibles Teaser: Mr Incredible vs A Belt. Simple and humorous.
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Monsters Inc ‘Charades’ trailer: An example of a fun way to compete against Harry P-.
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Ratatouille Teaser: My first introduction to Patton Oswalt, plus love Brad Bird as the voice of the waiter…and the texture/lighting of the cheeses and that jam.
Oh yes, I loved that one! 
Especially how at the end Mike gets up and barely even does anything, and then Sulley (who’s hardly even looking) just says “Star Wars” on the first try.
Yeah, that’s one of my favourites as well. One of the Monsters Inc trailers had “Break on Through” by The Doors as well. That was a good one.
^Omg, I have to look that up now!
Not sure if anyone brought it up yet, but I like this A Bug’s Life trailer. And it used Baba O’Riley by The Who. youtube.com/watch?v=vhGlMv3UCXA
I’ll wait to see if the list isn’t dominated by teasers. Although Trailer 1 & 2 for Wall-E is hauntingly memorable, and the Bug’s Life theatrical trailer really sells the film.
I adore Pixar’s teasers and trailers! Let’s see… where do I begin?
As far as teasers are concerned, my favorites are:
- Monsters, Inc. (I don’t know how many times I’ve just laughed myself crazy at that one. “Hey! Guess which planet I am!” “I’m going back to the break room before all the donuts are gone.”)
- The Incredibles (I think the reason for this is obvious… it’s so funny! And I admit I love Teddy Newton saying “Mr. Incredible. We. Need. Your. Help.” in that voice)
- Cars (I saw this one for the first time in a long time recently and realized that the opening was a ABL reference! That, and it’s just plain funny!)
- WALL-E (I love that they mixed in a little Pixar history into it, and that Brazil music will forever be WALL-E music to me!)
As for the trailers, I’d have to look at some of them again to get an idea. They’re all great, though the ones for Cars 2 stand out to me in particular. Maybe it’s because the trailers for Cars 2 seem to have the most unused animation and dialogue in it than any other. I mean, there are like, maybe four or five lines used in the trailers… I wonder why (Among them are “This place makes the Bermuda Triangle look like a kiddie pool”, “Mater, I’m sticking by you the way you’ve always stuck by me!”, “These Americans are clearly master spies”, and my favorite is Holley’s “Am I missing something?”). Maybe that’s why I watched the Cars 2 trailers repeatedly last year… oh, and they did a version of the first trailer entirely stop-motion animated with Legos! That was totally wicked! I’ll update on the trailers once I go through them again.
I’ve really loved some of their older teasers. Ones that let me know about the movie but told nothing about the actual plot. The teasers for Monster’s Inc, Nemo and the Incredibles I think are my favorites
Brave’s trailers were beautiful, in my opinion.
^Oh, definitely I especially love the “Family and Legend” trailer…
I’ve enjoyed all of Monsters University’s previews thus far.
As far as teasers go, my favorites are probably Toy Story 3 and Monsters University! Next would have to be The Incredibles and Ratatouille.
The Monsters University trailer is great, all my friends and I were cracking up at it in the theater!
Actually, the new short Monsters University is very nice as well.
Part of what makes the MU teasers so great is how they relate so similarly to the teasers of the first film. The traditional teaser and the “Charades” trailer are always good for a laugh.
I liked the montage they put in that Inside Out teaser. I also liked that one Inside Out trailer with the dinner scene–and I gotta admit, that “putting the foot down” part really cracked me up!
I also liked the latest Finding Dory teaser (and that living teaser poster they put up on their YouTube channel ).