Airline Seat Guide ($1.99)

Airline Seat Guide displays full seating guides for aircraft from most major airlines. Seats are rated by a color--green is good, yellow is average, red is bad--and you see the location of the galleys, closets, and lavatories. Use it to select the best seat on a flight since it shows the leg room (aka pitch) and width of each seat. It even displays which rows are missing a window (a particular pet peeve of mine).

Unfortunately, Airline Seat Guide doesn't tell you why a particular seat is bad; you just know that it is. The range of covered aircraft is pretty extensive and I like that the data for the most popular aircraft and airlines is stored directly on the phone. For the less common entries, however, you'll need an Internet connection. I've also used Flight Seat Guide (99 cents), but I don't like it quite as much.