My current game is a great example of why I love nethack. I am playing a healer and I have had really horrible luck with pets dying. What I needed was something… more powerful. Something that could eat those pesky shopkeepers and cross-aligned priests so that I can convert their stupid altars. 
Luckily, I found a polymorph trap. Since I don’t yet have magic resistance this was a lucky find (last time I literally stumbled into it and turned into a queen bee for about 600 turns). As I have yet to find a magic whistle, leash, or any way of controlling my pet, I constructed a rather useful fort of boulders…

The greatest part? This was after only my first try.