X-Ray mushroom. For a short time, allows you to see enemy weakpoints, hidden platforms/blocks, and secret passages, with a visual effect similar to Metroid Prime's X-Ray visor (take your pick, MP1 or MP3). It may not necessarily be located near any such secrets, so you may have to hit the block containing the X-Ray mushroom and follow it for a while before touching it in order to find secrets in some other part of the level.