To defeat the ice guardian in the "Shambala sanctuary" level you have to move this block in order to proceed. Thing is, I knew it was possible to move it out of the way, but I had a feeling it would take too long. Turns out it doesn't take too long, you just need to crawl to the wall. It should be slightly faster.

Here is a somewhat consistent way to skip the electric ball in Nub's Tomb. (Info in description)