favorite stock market simulator?

let's keep this quick and easy.

1. favorite stock market stimulator(s)
2. why?

before some of you have a heart attack -- i've checked the sidebar and wasn't able to find an easy solution, so i think this post is justified and i'd like your input.

here, i'll even give my 2 cents:

Think or Swim Papermoney - $100,000 of playmoney, plus you get to use their trading platform