A .NET decompiler written in .NET: I bet "let's try it on itself!" was not an uncommon thought among its users already.<p>It wasn't this one, but years ago I remember using a decompiler to look through things like the system libraries and the (relatively few) apps written in it at the time, and it was quite interesting how much metadata was available (if it hadn't been obfuscated). I think it's fun and enlightening to take things apart, see how they work, and modify them, so that aspect of .NET really appealed to me, but I still prefer native code for its efficiency and succinctness...