Up until Diamond and Pearl, I've always used Pidgey. Mainly because the first time I ever played Pokemon, back when I was a complete noob, I'd only train one or two Pokemon out of the six I carry with me. The toughest Pokemon I ever had was a Pidgeot, and when I got into the flow of things and restarted my game, I'd pick Pidgey and then when I restarted it again, I picked Pidgey. For some reason, I just really love Pidgeot.
But then, when Diamond and Pearl came out, I found a new Pokemon to spam; Shinx. Not only do I love the design on the little thing, it packs a punch and is worth training in my opinion. Luxio and Luxray are beasts when it comes down to it. ^_^