It depends.
If you talk purely about coding throughput, I know quite a few. Ayende Rahien/Oren Eini being one. That guy does most complex shit you can imagine, and does it well and fast.
If you talk about an 10x in any profession, You can see that in many walks of life, not just engineering. On many occasions, people find ways to do 10x impact with 1x work.
It can be closing a large sales, it can be avoid doing 6 months of work by 50 people by pulling 5 people for 3 month and approaching the problem much differently. Or it can be acting as a force multiplier by building tools to do grunt work etc.
So yes, 10x exists. even 50x probably possible to find, you need to stop thinking about 10x lines of code and start thinking about 10x impact. That can be your way to get to 10x.