I'm a former neteng and I'm having a really difficult time coming up with anything that is remotely interesting. I'm not going near running a Tor exit node.

With proxies and NAT I really can't think of a single thing I care about doing with tons of ips.. I feel uncreative here.

You could get into some form of webhosting but not everyone needs a public IP since apache/nginx proxy everything for wordpress and you'd just do hostname routing.

Selling the space either entirely or per block/IPs might be interesting since the price of IPs has gone way up.