Can't really say much on it... anytime someone asks I'm never too sure, so I just use what comes to mind first: Sableye. Sadly, I found it difficult years ago to use it past the fighting gym even when I tried to keep it. Might be different now if I replayed but anyway... I like that it has no official weakness (but of course it has weak stats to compensate for that...) and the design of it. Just, so much love. I find it very cute and creepy at the same time. And when I put one into Battle Revolution and saw this wide toothy grin it was capable of doing, I loved it even more. I think I even managed to see the anime episode it was in. Oh, and also, it's kind of like a treasure hunter... even though it would rather eat what it manages to find. A friend made a D&D campaign with a couple people and we got to play as pokemon (unfortunately it was short-lived) and I picked Sableye. Was pretty fun. Anyway... Even if I don't end up using it in battle much, I still like Sableye quite a bit. Uhm... as far as legendary... the first one that comes to mind is Suicune. It just looks so elegant and the design overall I guess appeals to me. I think one of the pokedex entries sealed it too. I think it was something about where it goes, the water becomes pure..? I know I always used it after catching it in Pokemon Colosseum, too.