All right, we are talking about must have apps? I'll chime in:
myWireless AT&T - you know the drill; I seriously use it to see how many GBs I'm using THIS month... retarded amounts of data have come and gone on my phone
AwesomeNote - because it's awesome and beats the snot out of the normal notepad
Navigon - a little GPS action; it's seriously an awesome app
Dictionary.com - I'm a writer, and I tend to write on my macbook, but when I don't have that handy or I'm writing by hand, this is much better than lugging around a bunch of books
The Weather Channel - cause I work at night and my day is all sorts of switched around, I never know what the weather is like
NeoGAF - haha
Facebook - the updates are glorious; I can interact with my fan page now and update about my writing
Echofon - was using it like crazy before, but I set my Facebook fan page to update my twitter account so...
Camera Genius - 4x Digital Zoom; big button; hold steady to take a picture; etc
BeejiveIM - connect to AIM, Yahoo, Gmail, Facebook, Myspace IM, MSN, Jabber, ICQ all at once; it's the Adium of iPhone
Dropbox - just set it up and now need to start putting stuff in it
Etrade Mobile Pro - because I do all of my investing through Etrade
Home Budget Lite/Mint.com - I got Mint first, but never messed with it; downloaded Home Budget Lite to see if it can replicate the way I do my budget spreadsheet; it seems workable so I might be using that instead
RedLaser - because it saved me $20 on a Wacom Bamboo tablet this past weekend
WootWatch - I check it every day... every... single... day... ugh
RepairPal - finding out if your mechanic is screwing you is always a plus
Urbanspoon - the commercials sold me on the phone; from that moment forward, I thought the thing was pretty damn cool
Yelp - the Alternate Reality stuff is actually cool and I'm going to use it on my vacation this weekend
Shazam - haven't used it yet, but I am going to the music capital of Ohio soon
Pandora - like finding out about new music
Mevo - a suggestion by a podcast; it's short but decent
Tetris - the wife really wanted it but without the original music we just don't get into it as much; still hella fun with the different modes
Peggle - this is on every device I own... I hate Pop Cap
SpeedTest - I like to see if my 3G speed has gone up; in Cincinnati, it's actually gone up in the last month, which is freakin' awesome