Javascript: Create a 10x10 array of 1s Obviously this challenge would be trivial with separate functions and libraries, so they aren't allowed. 

Your code must conform to an ECMAscript specification (any spec will do), so no browser-specific answers.

The array must be accessible after it is instantiated. 

I have an answer that I'll withhold for now. 

Note: this challenge is specific to javascript because it is notoriously inconvenient to make multi-dimensional arrays in javascript.
Javascript, 34 bytes
for(r=[b=[i=10]];i--;r[i]=b)b[i]=1

Since it's apparently OK to make the rows equal by reference, I guess it's apparently OK to rely on that fact. This helps us shave off one for-loop by building the table at the same time as its rows. So, here's my new contestant.
Since r[0] and b[0] are overwritten during the loop, they can contain garbage. This gives us another free execution slot to shave off some commas. Sadly, r=b=[] won't do, since then they are equal by-ref.
Also, it scales well (99x99 is still 34 bytes), doesn't require ES5 (the new functions have terribly long names, anyways), and as a bonus, it's unreadable :-)