The IIEQ is a free, fully parametric 10-band equalizer with its own, characteristic sound and low CPU consumption. The 1st and the 10th band are low and high shelf filters, respectively; all other bands are peak filters. Individual bands can be switched on and off (click on the small green buttons!). It is available for Windows (32/64 bit) and Mac (32 bit).
Weird alternative GUIs are available for Windows 32bit only.