I love a lot of pokemons, but my absolute favorite is Mightyena! Even though my friends still make fun of me for liking it XD
I actually used to like Raichu the most. But after playing Emerald for the first time 5 years ago, I just developed a lot of love for the pokemon.
Mainly because, as unlikely as it may sound, it worked beyond my expectations, even turning the tide of several battles that could have gone very badly. Especially the psychic gym..
And I like the design. Even though some people think its too simple, or even that it doesn't look enough like a real world animal.. Personally, I don't consider it to be a wolf or a hyena or whatever, but its own specie, a Mightyena! :)
Now, GF hasn't been really too kind to it, and neither were they to several Dark types. But, seriously some things just leave you wondering "what were they thinking?" and "how was that even necessary?".. The worst part is that looking at other sweepers that works well, its not really missing all that much, some pokemons are way worst off.
I still had my share of mini sweeps with it on X/Y though. Moxie is pretty fun to use coupled with a life orb, with some rocks and sticky web, and some strategy. But the life orb recoil and low speed can ruin everything, and its pretty hard to pull off.. :/