I know this is going to be unpopular but it has to be my phone. I can get weather reports, wind direction, river levels, migration reports (if you can believe them), sunrise/sunset times, hunting logs, navigation, sat views of vegetation, radio if it is REAL slow, web access to read the forum if it is slow, light for inside the boat if you can't find your normal one or the battieries ran down, camera, phone for emergency calls and work related calls if I've snuck out early or coming into work late, and so on.
Naturally, this only works when in range of a tower but most places I hunt have reception.
Other than that, it has to be my M1, and my Hoefgen with the mimi mud motor.
Mark W