Hi i am new in this forum. i want to know which is the best firewall??

Well, it depends if you are asking free firewall or payed firewall.
In general, the best firewall is the user. Meaning if you ahve a firewall, and you keep an eye out on what programs you allow and wich you dont.

I use Zone Alarm, and while its not best, its better than win7 firewall and its free. I just need to keep an eye out for possible programs trying to get in.