The default text editor on Ubuntu is GEdit. This is a problem because, unlike Notepad on Windows, GEdit is quite heavy and takes a second or two to start up. A lot of times during work, what I need is a super-simple editor to throw text into, edit it and use as a text buffer between copy and paste. I used to use Notepad for this purpose on Windows. However, editors like GEdit or GVim are too heavy and bloated for this quick-n-dirty usage.
Thankfully, there is Leafpad. This is a very minimal, very light text editor written using GTK. It has the exact same features as Notepad: nothing. So, it starts in an instant whenever I need it and is quick to use and move around. If you need a Notepad replacement on Ubuntu, try Leafpad. If you do not have it, it can be easily installed from the Ubuntu repositories using the package name leafpad.
Tried with: Leafpad 0.8.18.1 and Ubuntu 12.04 LTS