Basurao is pretty good... For killing anyways. XD He has a pretty high experience yield, which is odd for a fish. Probably matches Gyarados. He is a pain to battle with two great abilities, though.
Another good Pokemon for killing is Tabunne!! I mean the thing is pretty defensive, but it gives a bunchload of EXP~ Especially if your training a ghost type, it can't touch you. XD That's how I got my Shandera so fast!
Also on the subject of Shandera, that thing is AMAZING. That wicked Special attack kills!!
Pokemon I hate...
Definitely the Yooterii line. The, "well distributed stats" bastards is what I call them. They take a hit and then dish one out. (Take down hurts.) Which is bad if you are fighting them. Not to mentions the Intimidate as well, making them even more bulky...
Shinpera... Such an annoying type combination for some reason!! Mostly that dang flying... But yeah, with Magic Guard, my poor Chory (Tsutarja) could hard touch one! :c And with good speed and offense, and a annoying movepool....
Kokoromori. I just faced this guy like 3 times. Attracted. Then boosted with Calm mind. AND MY POKEMON WOULD NEVER ATTACK. DAMN LOVE STINKS.
Those are just a few examples of stuff I hate a like, could go waaaaay on. XD