Software of the month:
Ad-Aware from Lavasoft is a pretty good tool to remove adware. It is a must run after each browsing session. What makes it attractive is that it is free

Port Scanners:
Port Scanners are tools that scan the victim's computer for open ports. For more about portscanners read this.

KeyLoggers:
KeyLoggers are tools that record the keys that the host user types on the keyboard and can be configured to send it by mail to you.

Security:
All tools to protect your system. They include firewalls, antiviruses, anti-spywares and the like..

Miscellaneous:
Many hacking utilities which are a combination of many tools.