As a network geek inclined to bulk up on diagnostic tools, I liked how this little app adds port scanning and whois lookup to what I already have with NetTools. What makes Network Toolbox particularly valuable hides in its config menu where you can vary the size and number of pings; traceroute timeouts and time to live; and portscan delay, packet size, and range. A LAN tool also lists out the ARP table for the iPad -- useful but limited to your wireless connection.
Price: 99 cents
Developer: Wyllys Ingersoll
Compatibility: iPhone and iPad; iOS 4.2 or later