The fewer packs I buy at a time, the better the cards I get in them. (I mean, when I tested it out and bought a sole Legends Awakened pack, I got Uxie Lv. X in it. That's the first Lv. X I ever got in over a year. I'll buy them one at a time from now on!)
For the most part, I like the Rares that I get out of my booster packs. Most of them I can't really find a use for, but they're still fun to look at. But the Rare that annoyed me the most ever was Misty's Tentacool. I didn't buy may Gym Challenge packs, as I was very low on moeny at the time. I think I only got 5 Gym Challenge boosters total, and one of them happened to be Misty's Tentacool. I never figured out why that was Rare, as it didn't really do anything useful that I could see.