In DPPt it was my Staraptor. I just really enjoyed using it and I've never said that about a token bird evo line before. Usually I try to vary my team during each playthrough but I always get a Starly and keep it with me the entire time because I love using them so much.
Soul Silver was Mareep. 100% undeniably Mareep. I did an entire solo run with a Mareep and it was long, difficult, painful, and rage-inducing at times, but we made it all the way through together and I'll never have another bro like that.