Good thread! My brief thoughts on this:
Spritefont+. Getting the correct appearance of sprite fonts is easy with this and a pain with the stock plugin.
LiteTween / Ease Tween Mod or an equivalent, as discussed.
Paster / Canvas as well.
Full Box 2D physics behaviours. I know that rojo has done a lot of work with Chipmunk, but there are limitations and Box 2D runs just as fast as asm.js physics in chrome.
That's all I can think of really, the only other limits I've bumped into have been with my imagination or time available....