STL Viewer

It sports a really nice graphical interface with lots of features, but it doesn't have any editing tools.

Easy-to-use graphical interface with plenty of features at hand

STL Viewer doesn't come with a complicated graphical interface and it doesn't require you to complete a setup before you can use it. The software solution allows you to view Stereolithography files which describe only the surface geometry of a three-dimensional object without any representation of color, texture or other common CAD model attributes. The STL format specifies both ASCII and binary representations.
View STL files
The first thing that you need to do after launching the application is to open STL files from your computer. Simply browse all sort of directories on your device and open the files that you would like to check out.
It displays all sort of information on the image, like dimensions in millimeters and properties like volume or surfaces. In addition, you can check out mesh information and view axes and points on the figure.
More features and tools
Click on the image and scroll in order to zoom in or out. You can also rotate images and switch from the many views available. You can check out various sides of the figure, like the back, front, top, bottom or right view.
You can also switch between tile or cascade view and enable the wireframe feature. In addition, you can view the coordinates between each point on the figure. When you're done inspecting the image, you can save files in .png or .bmp format on your computer.
In addition, you have the option to create duplicates of the same .stl file. All in all, STL ViewerSTL Viewer is a very nice application for viewing and manipulating STL files.