First game, first time playing and I picked Torchic. I always liked the look of the fire types before I started playing, and this was no exception (seriously, that little thing is adorable).
On the second playthrough I used Mudkip, as a adored Swampert's design. There was a choice I didn't regret - Swampert destroyed absolutely everything.
I followed the same pattern with Emerald until finally giving Treecko a go. I was pretty happy with Grovyle, being the only second stage that doesn't look downright silly AND being pretty great visually, although, being perfectly honest, I was kind of upset when it evolved, Sceptile just wasn't the same.
Of all of them I definitely think Treecko is the most difficult to use, although it seems to have become more useful in subsequent generations with that Physical/Special split.
Never really was one for renaming.