Brand New was one of my favorite bands growing up and not much has changed since. I'm not a fan of some of their newer albums but Deja Entendu will always be one of my favorite albums of all time. I don't think The No Seatbelt Song is technically acoustic but it's my favorite "slower" song of theirs.
I love Brand New and this is my favourite Album from them. I still hear it on rotation on my iphone.
Anything Jessie J acoustic is great but "Who You Are" is so awesome!