javascript : how could a loosely typed, prototype-based, asynchronous language, with complex scoping rules, and a propensity for complex callback loops be possibly dangerous :)    

It does make for some fun surprises

I use the javascript console as a calculator, and it is funny when binary <- -> decimal rounding/conversion errors pop up unexpectedly.

This is a good reason to be careful when doing if(x==someNumber) conditionals in your code.