World 2 - Level 7
First get the two powder kegs to the white "X"s. The top-right one should not be too difficult, the second one will require you to use both alcoves marked with a yellow "X". But either Stinky or Loof into the alcove to be able to push the keg away from the wall, into the white teleporter, and then toward the white "X". Obviously the alcove in front of the cannon will require quick timing. This second powder keg will be detonated by the cannon, freeing the Rainbow coins there.
To detonate the top-right keg, position Stinky at the green "X" and use Loof to push the boulder along the green arrow. Next, push boulders along the blue paths (left first, right second, middle third). Move Stinky to the purple "X", and use Loof to push the boulder into the black teleporter. Stinky can now push the boulder into the second powder keg and detonate it.