All the kids around here are using this thing called "Sublime".
Up to now, I use a combination of nano, vi, gedit and texmaker depending on what I'm doing.
Now that I'm writing up my thesis, however, I am transitioning to gvim. It took me a little bit of time to get anything done, but it doesn't take long before it becomes really useful.
So, what do the rest of you nerds use?