My favorite is the opening scene of Bolt.
Favorite element of that is when the humongous explosion happens and it pulls out to a shot across the river to a park bench with an empty coffee cup and it tips over, so after this humongous explosion you hear this tiny tip-over of an empty paper starbucks cup. I laugh every time. This You-Tube video has it at 2:45.
http://www.youtube.com/watch?v=k-WzN1jCnMM
The two cats who haze Bolt in his trailer...
The pigeons - my god the acting and stereotypes for the voices as well as the pigeon sound effects were great.
Then the sounds of the hampster's roller ball. The air-tight seal when he opens it, etc. etc. etc. You have to see the movie - comedic timing and sound effects are great.
But then again, there is always Up. I loved the kid's clunky boyscout attire and the bird's sound effects. I also loved the voice treatment on the big mean guard dog and Doug's voice. I love how the leader of the dog's voice gets pitched up too high when it malfunctions and he loses his intimidation.
Oh yeah - and then there's the little guy in Ice Age who's always chasing the acorn. (I don't know it's name or species - forgive me, Mr. Thom).