You prompted me to vote: My choice has to be my 1st gen iPad. I have a 3GS but it serves as a secondary phone until I purchase the next iPhone, so without a doubt my iPad is the tech device that I would not want to live without.
My ACD, to my surprise, is a very close second in this category.
iPad 2 I do everything on it since getting it and my MacBook Pro hardly gets used these days.. That will all change when I start back at University after the summer though.
My iPad1 16GB Wifi, seriously handy piece of kit, especially as my MacBook Pro is often wired into a display etc, so if I need to get on the move asap, the iPad is the perfect tool!