Hmm... the power lines and things are true, but there's a few more.
The biggest one would be the bad guy's jeep that goes over the side of the train trestle (bridge) near the end of the episode -- it was totally missing it's engine & transmission! An eagle eye will notice this just before just before it rolls over the edge, but it's clearly visible that the engine bay is empty as it flips over at the bottom of the hill. Poor old jeep.
Then we have the rat. Do you really think a wild rat would behave so nicely when someone lassos it with a string? I don't think so, Mac would have been victim to a rat-attack. It was a cool little trick though, so it's ok.
Lastly, the "freon" canister Mac used to break to lock. Freon is not the same as liquid nitrogen, it would NOT get anywhere near cold enough to break metal (I use to work in heating & air conditioning and I've gotten it on my hands before, so trust me). Freon also dosn't just sit in a little canister, it's found in the entire system, including all the lines and hoses. What Mac had there was really just a line filter, and I gotta say that was the *largest* line filter I have *ever* seen, not one you'd likely find on a "small refrigerator".
It all plays out cleverly though, so these things don't really matter, it was still a good episode.