[Auvdar]

The skeleton key you mentioned is the only thing I can think of / remember. Might be a few others.

However I will tell you one thing. Wont spoil it, but if you play the Dragonborn DLC that came out, make a few back up saves before even going into the final dungeon (you will know when you go into it..).. Unless it got fixed, there is a huge game breaking bug during the last fight that can get you stuck. and afaik you can't /console kill him either, since it's all scripted and you basically get stuck. I had to turn all mods off (which included the armor and weapons) which got the fight to work, then had to turn on God mode just so I could actually kill him (since I was naked).

There is another bug like this with Dawnguard, where a NPC you need to follow you goes aggroe and won't break (and you need him to further on the story, so you can't kill him. He just comes back aggro..)