I love the grottoes, and in fact logged in here today for the first time in quite a while specifically because I had a great grotto story and nobody else can appreciate it.
I'm replaying White 2. I started with Tepig, just because I've used Oshawott too many times and I can't stand Snivy, but I didn't want to keep Tepig all the way through, mostly because I plan on picking up a Camerupt when I get the chance. But that meant I needed a Fighter. I didn't want Lucario just because it's too good and makes the game too easy, and I didn't want Scrafty for pretty much the same reason. I considered a Sawk, but it doesn't show up until too late in the game, and I just did a playthrough of Black with a Mienshao and didn't want another, so... I just wasn't sure what I was going to do. But I just went ahead and figured I'd sort it out along the way.
So I got to Route 4 and went ahead and caught a Scraggy, just in case (and a really good one at that), then beat Elesa's gym (with a Trapinch that I'm going to retire when I get a Camerupt). On my way out of town and Bianca shows me the Hidden Grotto on Route 5, and I went ahead and caught the Minccino, then I thought "Eh... what the hell," and went to the Hidden Grotto in Lostlorn Forest. There was a brief moment as I was walking into it when I thought, "You know... it would be really cool if..." and there it was, before I could even completely frame the thought - a Moxie Heracross, just sitting right there, waiting for me.
So I've got all the Fighter I might ever need now, and then some. It's still sort of the same problem as Lucario or Scrafty - Moxie Heracross is going to make the game pretty easy - but that's okay.