I can't believe no one said VLingo.... If I could only have one app... it would be VLingo... voice control over most everything, voice type into all other apps, hear SMS and/or emails when arrive... send SMS emails without typing... works through headset perfectly... a truly amazing app...
I think I really only use 3 apps that aren't stock, and those are Bejewelled, Mahjong Solitaire, and Facebook. Other than that I use my browser more than anything else.