iplist is a Linux application for blocking connections to and from a specified range of hosts using the netfilter netlink-queue library. Iplist is an open source IP filtering program similar to PeerGuardian for Linux
What need would a penetration tester have for this tool?
None really. If you're at the point where you need to be sure you don't scan particular IP addresses (a known SCADA system for e.g. was filtered to be sure it wasn't knocked down accidentally), you should be well and truly at the point of knowing how to use iptables without some skiddie code to help you out.
I vote no to this tool. If you desperately need it, you can figure from instructions on the site how to install it anyway.