It's probably already discussed, but I find it annoying that you can't Sweet Scent in rain. I mean, I think I understand the logic behind it (the smell being dissipated by the rain and all), but it means that if I want to EV Train Pokémon, I have to do it elsewhere, where the encounter rates may not be as favourable. Take Special Attack training for example. There is only one place in OR/AS where every horde you encounter guarantees Special Attack EVs; this is Route 119, where Oddish has a 100% chance of appearing. However, almost all the time, this route is covered in rain, which means that I have to go elsewhere to train, such as in Route 112 where Numel hordes are only 65%, or Route 120 where Oddish hordes are only 60%. It takes a lot longer to EV train when this happens, even though I do get it done eventually.