Mmm...chocolate Guinness cake. I use Nigella's recipe and it's always a sure hit.
I also saw someone mention cake batter cookies. I was skeptical about these but made red velvet ones at Christmas time covered with icing sugar. I AM HOOKED.
More "American"-ish desserts (at least I think they are) that I love:
Pineapple upside-down cake
Blueberry Muffins (this is the best recipe ever:
http://www.manilaspoon.com/2012/09/blueberry-muffins.html)
NY Style Cheesecake (I have a Jamie Oliver recipe somewhere that is spot on)
Pumpkin pie (I'm pretty much pumpkin obsessed)
Sweet potato pie
Key lime pie
I am happy to taste test anything. you know, to make sure the new mixer is mixing properly and stuff. :-D