cannon room bug in twilight princess - will destroy the save file! - spoiler, but helpful!
in kakariko village (after you restore the power in the dominian rod and get all 6 characters, the room is in the basement of the shaman's sanctuary near the entry to the graveyard behind a statue that is moveable with the dominian rod) remember to talk to Shad and get him to leave the room before you save! if you enter the cannon room in the basement and save before shad leaves and then turnthe power off, u will be stuck in the cannon room forver! with this glitch, what happens is when u return to the game, shad is supposedly gone (ie: you can't see him). however, the game still thinks he is there and will prevent u from leaving and midna will not let u warp the cannon to get to the city in the sky. in fact, shad will talk to u, but the background is from the room above. it may get repaired at some point but as of right now, i know nothing of this matter! a good place to check may be the nsider forums on the nintendo website.
if you want to see the glitch in actoin, the entire thing is explaind in this video on youtube.com: http://www.youtube.com/watch?v=JiWa7_ZQ_EQ