There are some chests in Nightfall which you can open without using a key.
You'll get some money (between 1k and 3k) and a Golden Item or a Diamond/Ruby/Sapphire.

I'll post the link below

http://gw.gamewikis.org/wiki/Do_Not_Touch

Hope you have fun with these chests like me :P

Note: The Chest in Domain of Pain is very hard and well protected