Don't forget PilotWizz Pro. It can live on either your iPhone or iPad. Probably more use on the iPhone. Great for getting TAFs and METARs on the run and a very nifty W&B calculation app. With the ability to store data on all your regularly used aircraft it means you can do W&B with one hand and have the fuel nozzle in the other!
Also use Air Nav, Memory Map and Logten Pro on a regular basis although once again I find Logten most useful on the iPhone.