In colluseumn you can get a Misdrevus very early in the game.My favourite pokémon types are Fighting, Psychic and Ghost. Fighting and Psychic types are pretty easy to get one's hands on, and a few of my favourite pokémon are comfortably slotted into both criterea. Ghost type pokémon are the only ones I ever have problems getting around to, because the majority of them are often obtainable late into the game. And by the time I do get around to capturing them, I've usually got a team on hand that I find works well and I wouldn't want to disrupt that perfect balance. The only Ghost pokémon I've ever bothered to level up all the way to the big one double zero is Misdreavus back in GS, and that was only because I had time to burn.
I don't really have any pokémon that I'll use in every game, as I'm usually all about experimenting with the new. I do have favourites, but I prefer experiencing something new~ But since buying Sapphire, I always make it a priority to have a Combusken on my team, for obvious reasons. I'm planning on using the Global Trade Centre in DP as soon as possible so I can actually play through the game with one on my squad of six.
My favorite type is Bug, but unfortunately, I haven't mustered up the courage to actually make a Bug team exclusively.