As the title says, which Pokémon do you carry always with you? The one that always has a space on all your teams, across every generation, no matter what? Mine is usually Heracross
With each generation and playthrough I strive to use Pokemon I never used before, so I don't have a species of Pokemon that stays on my team for every generation. If I had to choose, it would definitely be Nidoking.
My HGSS Surf-chu in Black, had to delete surf to port it over, but maxed out ATK and SpA IVs and Hidden Power Ice is too valuable, so I cloned it and ported.
It's usually Crobat, because it was the only flyer that I liked the look of but now I like Golurk, Thunderus and Volcorona better so he doesn't have a place on the team (sorry Crobat). I usually have my starter aswell.
Arceus, because it's the most highest level that I own, and I like watch it battle with wild pokemon and saying:"Oh, you just hurt a god! now prepare for revenge!"
My first EVd pokemon, My wailmer... Don't ask I used to be dumb. But nor, thanks to eviolite I can use him for the first time ever! And I've had him for five years