In the necessity of an image editor, constraints to utilize resources of my machine and speedy startup time of the tool made me to google around the web, after many trails, finally i ended up with paint.net.
This is a free Photo editor tool written in C# with by Rick Brewster, Tom Jackson and others, it is a highly portable, heavily loaded with features and is best at performance. The installation package at 1.47mb is the most appealing compared to the whopping 100+mb of most famous Photoshop. Though it may lack some features of the latter, it is definitely a powerful editor to work with.
The learning curve is very low, thanks to its tutorial forums. Here are some features in brief. Ability to edit with layers, predefined set of special effects, unlimited history to undo changes and powerful tools such as magic wand and gradient tool makes it distinct and more unique. The most exciting thing is, its Open Source. Code is available under MIT license for free. Being a .NET professional, i am very much interested in its code. A great application for learning many things.
Wanna try it ? then it can be downloaded here.