Specifically one that delivers hot guys to my phone. I have my new shiny the HTC HD2 and while it's not an iPhone or Droid based (still runs windows mobile) since I'm nowhere near a power user, I'll do fine.
But there are some sorely missing apps...like one that would take me directly to my Xtube favorites. What's the point of a small, hand-held internet connecting device if you can't watch porn. And while I can surf the net for it from my phone, the whole secondary interface thing is a bit of a PITA. Because otherwise I'm tethered to my desktop or laptop. But surfing porn form anywhere and the sweet one palm free access. It's built for porn.
There is an app for mixing cocktails. Frankly though that's what bars are for. Although a friend swears there's a craigslist type hookup app which I guess makes bars passe.
And an eBook reader. I know there's tons of that type of app...but one that will tell me before I get to deep into reading whether the book sucks or not.
I could probably think of a few more, but still, what do you wish there was or what do you use all the time that's cool?