So, I know EVERYONE'S been talking about Toxic... I just ran through all 30 pages, and the only thing I've found is the usual "Toxic's accuracy is perfect if you're poison" and all that. However, I was in the Battle Institute and found one more interesting quirk regarding Toxic (and I'm pretty sure this didn't happen in BW).
I was using my Gliscor (what's up, Its_A_Random?) who had the usual set; Toxic, Substitute, Protect, Earthquake, all with the Poison Heal ability. I was battling some flying type (I don't remember who it was, I believe it was a Mandibuzz), and it was spamming Roost. Normally, this wouldn't be a problem. Toxic keeps building up more and more damage and eventually it'll take out your whole health bar, regardless of how much you heal.
But that didn't happen. Whenever Mandibuzz used Roost, Toxic would do the same damage it did last turn. That is, Mandibuzz tried to use an attack, Toxic did 1/16th damage. It used another attack, it took 1/8th damage. It used Roost, and it took 1/8th damage at the end of the turn again. My only hope was to continually stall, since it would only double damage on the turns it didn't use Roost. I'm certain my eyes weren't playing tricks on me, because this stall lasted a long time. (And since I was faster, I couldn't EQ on turns when it used Roost.)
I started to get worried that Toxic had been completely nerfed (that it wouldn't double if the Pokémon had ANY recovery), so I tried it against everything. Pokémon holding Leftovers do not get this luxury. They can survive a little longer, sure, but Toxic still increases exponentially.
The fun part came when I was battling a grass type with Giga Drain and Ingrain. Even with both of those, neither of them stopped Toxic from doubling up its damage each turn, so I was able to outstall it.
It seems this only happens with dedicated recovery moves (Roost, and I'm assuming Recover, Slack Off, and the lesser used Synthesis, Moonlight and Morning Sun). Unfortunately, since this happened at the Battle Institute, I couldn't save a Battle Video, so if anyone can do some testing, that'd be great. (Maybe I am just crazy!)