a few of mine are:
dish network app - i like being able to set recordings and delete shows from my dvr from my iphone/ipad. i've been thinking of getting a sling adapter or upgrading to the hopper so i can watch shows that are on my dvr on my ipad when i'm away from home.
apple tv remote app - i use this rather than the standard remote to control my apple tv. very easy to use.
iControlAV remote app for pioneer avr - i have a pioneer elite vsx-60 avr and this app lets me control every aspect of it. i can switch zones, switch channels, change input/output modes, change the volume, etc.
wifi transfer app - i use this to quickly transfer files between my iphone, ipad and computer. i can go from iphone to ipad, ipad to iphone, iphone to computer, ipad to computer, computer to iphone and computer to ipad. i use it mainly for pictures, but you can send videos as well. i like it because i don't have to hook up my iphone/ipad directly to my computer to transfer pics/vids.
mahjong - excellent time waster
skee-ball - another excellent time waster
espn scorecenter app - i have mine set up to send me alerts with scores on ALABAMA games (all available, not just football)
and i've been thinking of calling adt to see how much it would cost to get the remote control ability and app for our security system. i'd like to be able to check it when we're on vacation or away from the house for an extended period and enable/disable it if necessary.