RS-MET has released EngineersFilter, a freeware VST plugin which implements several scientific filter designs.
These sort of filters with extremely steep slopes are certainly not the best choice for everyday EQ tasks, but as a sound design tool they can do wonders. Lots of fun to experiment with these! Here’s more info about the plugin:
Engineers Filter is a filter plugin that allows for extremely steep filtering. It achieves this by implementing high order IIR filter design methods that are commonly used in science and engineering, namely Butterworth, Chebychev, inverse Chebychev and elliptic (aka Cauer) filters. Each of these filter design methods can be applied to create lowpass, highpass, bandpass, bandreject, high/low shelving and peak/dip filters of orders up to 20.
I suggest you check out the RS-MET pages for more unique and useful tools like their pretty cool Signal Analyzer VST for example.