How to create Cell-shading effect like the game borderlands? Is there any BGE examples around?
Cell shading is done by setting the specularity mode in the material properties to toon. The outlining is done by a GLSL shader. Also, In boarderlands, the textures were stylistically drawn by hand to mimick the visual style of a comic book.
TOON materials would be enought and some nice hand made textures
Alright, found it.
Demonstration: 
This is pretty much the same shader they use for their series.
Edit: Forgot to add the shader like an idiot… 
shader:
/**
* Toon Lines shader by Jose I. Romero (cyborg_ar)
*
* Based on blender's built-in "prewitt" filter which is free software
* released under the terms of the GNU General Public License version 2
*
* The original code is (c) Blender Foundation.
*/
uniform sampler2D bgl_RenderedTexture;
uniform vec2 bgl_TextureCoordinateOffset[9];
void main(void)
{
vec4 sample[9];
vec4 border;
vec4 texcol = texture2D(bgl_RenderedTexture, gl_TexCoord[0].st);
for (int i = 0; i < 9; i++)
{
sample[i] = texture2D(bgl_RenderedTexture,
gl_TexCoord[0].st + bgl_TextureCoordinateOffset[i]);
}
vec4 horizEdge = sample[2] + sample[5] + sample[8] -
(sample[0] + sample[3] + sample[6]);
vec4 vertEdge = sample[0] + sample[1] + sample[2] -
(sample[6] + sample[7] + sample[8]);
border.rgb = sqrt((horizEdge.rgb * horizEdge.rgb) +
(vertEdge.rgb * vertEdge.rgb));
if (border.r > 0.4||border.g > 0.4||border.b > 0.4){
gl_FragColor.r = 0.0;
gl_FragColor.g = 0.0;
gl_FragColor.b = 0.0;
gl_FragColor.a = 1.0;
}else{
gl_FragColor.rgb = texcol.rgb;
gl_FragColor.a = 1.0;
}
}
Thank you all for the info and help.
Anytime! 
No problem! 