>>14128168I have three, which I know sounds stupid, but there's a good reason for it. In no particular order: Electivire, Swalot and Alakazam.
Electivire (Wattson) became my Bro in White 2, and I've raised him into the late 80's. He's been very reliable throughout the game and I plan to move him up to X.
Swalot (Miasma) is my 3rd gen bro (technically not a "bro" cause it's a girl), I was on Pokemon Showdown and I thought it would be cool to make an all poison NU team. I ended up using Swalot and he soon became the most reliable Pokemon on that team, so when I decided to replay Ruby I caught one and she's been able to take down Pokemon more than ten levels higher than her, yawn is evil and I love it.
I've had an Alakazam (Astro, Astral, Cosmo, Apollo, ect...) on my team since 3rd gen, I catch an Abra in every game I can. His speed and high special attack has won me more battles than I can count. I prefer to get a new one each game, so he's not going to be transfered or I'd have an entire box of them... I can't say I like him any more than the other two, or that I have a favorite among them at all.