It's too hard to pick one from every year but that's how I have it.If I had to pick one for each...then...
2 - App Store
3 - Copy and Paste, MMS
4 - Multitasking, FaceTime, Folders and HDR
5 - Notification Center Siri
6 - Maps
Siri came out in iOS 5, not the iPhone 5Siri didn't come with 5 Just came with the 4s