GTS Negotiations was the best thing to ever bless Pokemon, I used it more than most of the post game in BW and BW2

The trade system of BW where you can show several Pokemon was perfect, and the comunication method we had with Faces and Hearts was actually fun to use and fast, unlike Gen 6 nicknamed Pokemon, or preset sentences (it takes longer to choose them)

ITT: Great ideas from Gamefreak that were scratched for no reason