Here's one of the earlier projects I've worked on. The motivation, well more like an excuse to make a game, was the RIT SSE game competition. We took up the challenge and the rules were simple. It was just to make a 2D game for an arcade cabinet.

Mica2D is a game engine (my first ever) developed by Colin Doody, Brian Johnstone and I. It is an entirely 2D engine, but utilizes some normal mapping technique to give our 2D sprites a 3D feel. We used OpenGL for the graphics engine. Some of the features include shader materials (GLSL), sprite particle systems and post processors like bloom. The engine also integrates Newton Physics, FMOD and Lua scripting. The whole thing is then tied together with the Odyssey framework which was developed by Brian.

While things like 2D lighting is a fairly common thing with deferred shading nowadays, I thought our engine was quite powerful during that time.

Here are some links & references:
Brian Johnstone & Collin Doody: DarkwindMedia
Deferred Shading (GDC 2004) - Just a little note on deferred shading. When doing deferred shading in 2D, there are a lot of assumption you can do, so you don't have to do all that extra stuff.
NVIDIA Plug-ins for Adobe Photoshop (Normal/Cube Maps, DDS)