AFAIK in an Auto you can't "Lock" the key unless it is in park.

Manuals, yea - you would have to be careful not to turn it all the way back...

 

I'd say in a manual transmission vehicle that shouldn't pose any extreme danger. Just push the clutch back in and let it bounce off the rev limiter. Granted it could increas your reaction time by the second or so that it took you to realize, thus making accident avoidance more difficult.

My 95 Nissan Maxima's floor mat clips never held on too well and the floormat on the driver's seat would eventually come unclipped and start creeping up toward the pedals until it would eventually get in the way of the clutch. Never the gas, but the clutch - it was really annoying so I eventually just took it out completely.

 

Wtf? We're talking about a gas pedal stuck on the carpet, not a binded throttle cable or anything.

Either use your toes to dislodge it or reach down and pry it loose. Either solution will solve your problem quickly.

I was valeting a Jeep Wagoneer once and the actual cable got binded at almost WOT. I reached down and tugged on the gas pedal a couple of times, couldn't have taken me more then 3 or 4 seconds, but I snapped it, the engine returned to idle, and I cruised it back.

Luckily, turning off the engine will work fine on an efi car, but if it's carbed you're screwed. The damn thing will diesel on forever.

 

I swear officer, my gas pedal got stuck!

 

My toyota's carpet is perma-clipped and I can't take it out.
I also apparently have back-up brakes?

 

My 95 is that way too.

 

Turning off the key will stop the spark. If it does diesel on after that, you should be using higher-octane gas.