1. Facebook
2. Sportacular
3. Twitter
4. Google Earth
5. Youtube

But since i updated mine to IoS7, the youtube was lost.

Onavo extend. It compresses the data to save you money on your data plan.

My Radar Pro. (Great wx app for almost every leg)
The night sky.(Stargazing,etc. Just point and identify)
iStart Spanish.(50 great lessons for only 5 bucks.)
First Aid.(Just in case)
Photosynth.( Great picture app)
Fidelity. (To track that 401k,etc.)
My boxing pro.(When the hotel gym is lacking.)

Aeroweather and Foreflight!

Big fan of Aeroweather here too.

Flightboard. It updates real time with the airport boards.

I also use flightboard. Very accurate.

I use Yelp on layovers. I enjoy hiking a little to find mom and pop type restaurants for good reasonably priced food. It has lots of options to sort local restaurants depending on what you're looking for.