I've seen this idea blogged on several times in the past, I think on Nate Teodoro's blog and Charlie James' blog and Chris Marshall's blog - but I'm too lazy to chase down the URLs for you. The idea that if you want to see what the most useful techniques would be in a real street fight, look at the actions that are illegal in any combat sport.
Take Judo for instance, If you look at the IJF judo rules, section 27 - Prohibited actions and penalties, you will see that what is illegal in judo includes...
- To intentionally avoid grabbing the guy - and not letting them grab you.
- To avoid attacking the guy, or to try to get away from them
- Endangering small joints or spine (neck cranks, finger locks, wrist locks, leg locks)
- Grabbing their legs
- Touching/hitting the face, kicking
- pushing the opponent out of bounds
- squeezing leg scissors
- entangling a leg and falling onto it
- lifting and dashing them against the ground
- falling while applying jointlocks (like wakigatame) or falling/bridging backward into the ground with them on your back
- wearing/using hard metalic objects
- and of course, such non-sporting actions as poking, gouging, ripping, biting, spitting, head-butting, groin attacks, etc... fall under the category of "against the spirit of judo."
Typically we like to think of the aikido that we do as self-defense judo. That is, all the stuff that is illegal in judo contest, we try to find a way to practice in aikido. So, in aikido you see lots of hitting/pushing the face and a wider variety of jointlocks than you see in judo. You also see good taisabaki and gripping actions that deny the opponent a grip/position.
But there are still actions in the above list that our aikidoka are probably unfamiliar with. Might be worth going through this list and finding a way to safely and carefully and systematically give aikidoka some exposure to some of these situations.