It was a pokemon like this that made me realise my strategy to narrow it down to 50 was a lot like how FIFA narrow the football teams down to 32. They may not be the best but they are the best to represent the whole world. My list is like that. There are no more than four of any type of pokemon on the list, not including secondary typing.
So, let's talk about why Koffing is in my Top 50. Poison is quite an unpopular type for me as it is famous for bringing out some of the ugliest and most disgusting pokemon ever. Koffing is probably the only pure poison pokemon that looks happy. Other Gen I poison types look like their in a living hell; exactly what I'm in when looking at them.
Koffing is simple but interesting. A purple landmine that lets out toxic gas. It is just a design that can't go wrong. Simple but not boring, unusual but not daft. Its unique style is what won it over main rival Arbok. It wasn't until recently I found out Koffing was probably a landmine, whilst even in the days of Red and Blue you could tell that Arbok was a cobra. That shows its design was too obvious.
My final note will be on its name. Koffing is one of those names they could only get away with in Generation I. It's simple whilst just bordering on silly. It is one of few pokemon to demonstrate that evolution isn't always good and two heads aren't always better than one.