For me, Substitute / Magnet Rise / Thunderbolt / Hidden Power Ice Magnezone is such a godsend in this metgame. A lot of the things that counter Latios, Garchomp, and Shaymin-S (Bullet Punch Scizor, Bronzong, Scarf Dragons) all gives Magnezone a free switch-in and a Substitute up. And the only thing in the current metagame that doesn't get completely fucked up by a Magnezone behind a Substitute is Blissey and the rare HP Fire Magnezones.
Speaking of which, Substitute is such a great move to have right now. Not very useful against stall, but I find that most of the offensive teams rely on being able to switch into NVE moves and get absolutely devastated when they have to take a hit.
As for the suspects... Shaymin is devastating. I wasn't around for its first suspect test, but it is such a great offensive Pokemon. I'm really wondering why there are barely any Heatrans, and even then they are rarely holding a Choice Scarf. Not only that, but it can come in on Garchomp and Manaphy (though the latter I find always subs first, so maybe not Manaphy).
Garchomp just gets shit on by the other suspects. Yachechomp just gets called a slowpoke by about half the metagame right now, ScarfChomp just gets either Levitated or walled by a Steel and owned while Outraging. I haven't seen any Chain Chomps or whatever, but I do think it would fare better than the former two. I personally like Sub+Salac, forcing the opponent to either get swept or bring in their Scarfer / Scizor and get punished on the revenge. I'm thinking even without Salac Subchomp would work wonders.
Latios. I have had very little experience with this one actually. Almost all of the ones I've seen run Scarf's, which is so easy to stop. Any other set, I'm scared of...
Manaphy. I run an offensive team, which absolutely tramples Manphy so I can't really say much about it. Thank you Shaymin-S for your ridiculous speed.
DX-S. A giant thorn in full offense, but otherwise I honestly don't find it Uber. Without a 4x SE attack it does completely shit damage. Lead is just sort of whatever. I don't know. Not very experienced with this one, or at least not experienced in getting screwed by this one.