Level 1:
Sometimes when tossing a pot at the area highlighted in red, and various other places along that sandbag wall, the pot will break without hitting the switch:
http://i41.tinypic.com/39aj8.png

You can walk through the large gear near the lift to the next level, this problem does not affect the destroyed gear in the 3rd level:
Standing at the gear: http://i43.tinypic.com/24wdqmc.png
Walking through it: http://i39.tinypic.com/2cbuxi.png
Charging my bomb to show I am inside the wall: http://i44.tinypic.com/wsp5wp.png

Level 3:
You can walk through the energy turrets, if you walk through the middle one the battle will start without anyone having to go through the one way force fields:
http://i42.tinypic.com/fypil1.png