Top apps: Productivity, Office suites
As cute of a program as Microsoft Paint is (*cough*), you'll probably need something with a little more weight if you intend on seriously editing or designing any images. The obvious choice for this matter would have to be Adobe Photoshop, but unless you have $700+ to throw down, it's probably a bit impractical for basic edit jobs.
You will found something more financially viable in the GNU Image Manipulation Program, more commonly known as GIMP, which can be had for nothing. Paint.net is another free alternative to Photoshop that many people rely on, though its development has slowed down in recent months.
For something around the middle, we typically call upon the graces of Adobe Fireworks to accomplish our image related tasks.
If you're doing anything more significant than typing up a grocery list, it's likely time that you come to the side where grass is greener and either invest in Microsoft Office or download a free copy of OpenOffice.
There is no true “pick” here. I’ve personally used both extensively and have no complaints about either, although after using OpenOffice for lengthy periods of time (over a year in some cases) I always crawl back to Microsoft Office for no specific reason. For the opinions that aren’t already set in stone about the suites themselves and their origins (private vs open source etc.), I’d truly recommend using both to find what works best for you.
Advanced Text Editor
If you’ve got cash burning a hole in your pocket UltraEdit is probably the best potential candidate to fill this role whereas Notepad++ is free and is probably more than you’ll need.