_____Hmmm...well, many people like MMORPGs, multi-player giant online shooters like TF2 and CS:S, but I want to mix things up, even if not much. I'd at least make the most realistic physics engine, just because I like them and enjoy physics itself. I'd then go about making a health system. You know how most games just have a health bar, where u take the same damage no matter where you are shot, sometimes the head is critical, but other than that bland. I would make a system based upon the condition of the body: major organs, blood loss, broken bones, severed nerves; even the smallest ailments like headaches and a twisted ankle can effect the character. You can't just slap a bandage on it and make it okay. Sure, you can put some gauss on it or wrap it in a splint 'till you get to the hospital, but you can't survive with 6 broken ribs, and a collapsed lung. I would then, after creating these engines, figure out a game to apply them to. Multi-player could be applied, but I'm going to stay away from that for now.
_____Perhaps...a first/third person shooter. Not really third person, be sight would be different. You can see you nose if you try, you turn your head to look, not your whole body, the screen is even fuzzy around the far edges of the viewing box, as everyone knows that when you look at something, the surrounding area isn't crystal clear. You would see a great deal of your arm, as any real person doesn't hug their gun close to their face. You remember that physics engine I mentioned earlier? Well, I'd use that to create realistic weather. It could shine, rain, be overcast, snow, and a million other combinations and things I didn't mention. Ironsights, watch checking, looking in to the sun can blind you temporarily, or permanently if you look into it too long. Basically you in are the most realistic simulation of the world. If anyone can think of a good single player, fps, please comment.