Fieldrunners for iPadiTunes link: Fieldrunners for iPad - £4.99
Considering its £429-plus the price, it's probably fair to assume no-one will be buying an iPad solely as a gaming system. Certain genres of game, however, do lend themselves fantastically to the tablet format, especially tower defence titles. And for our money Fieldrunners is the best of the bunch.
The graphics look fantastic, helped in part by their saturated colours and cartoony style, and only improved by the vibrancy of the iPad's display itself. The gameplay is hardly revolutionary (although Apple would probably claim it as so going by the iPhone 4 hype) but it's astonishingly addictive.
Fieldrunners succeeds for the same reason MMORPGs are so popular. Despite 'gameplay' consisting primarily of watching animated towers kill animated enemies the game fosters a constant desire to complete just one more wave before quitting.
Even once you've unlocked all of the available maps and gameplay modes there's still plenty of fun to be had trying out new tower arrangements and strategies. It's the gift that keeps on giving.
There are other (cheaper!) tower defence titles available but when we have a bit of time to kill it's Fieldrunners we keep coming back to.