PRO HACK

Angry IP scanner is a very fast IP address and port scanner. It is widely used by network administrators and just curious users around the world, including large and small enterprises, banks, and government agencies. It runs on Linux, Windows, and Mac OS X, possibly supporting other platforms as well.
Angry IP scanner on Linux and Windows XP

Angry IP scanner on Mac OS X and on Windows Vista

It can scan IP addresses in any range as well as any their ports. It is cross-platform and lightweight. Not requiring any installations, it can be freely copied and used anywhere.
It can scan IPs in any range, even 1.1.1.1 to 255.255.255.255. Its binary file size is very small compared to other IP scanners. Angry IP scanner simply pings each IP address to check if it's alive, then optionally it is resolving hostname and tries to connect at specified in Options dialog box TCP port.
It also has additional features, like NetBIOS information (computer name, workgroup name, currently logged in user and MAC address), results saving to CSV or TXT file, can be used as a command-line utility in a batch file, etc.

Pros: TINY program. Easy to use interface. No installation required. Freeware. Does any more need be said?
Cons: Till Date none :)
Overall: Its a swissknife as compared to others,small,free and deadly.Its an very highly recommended for network admins and apprentice hackers and computer nerds. get it,and get it fast
Download It here