Voodoo2s are popular because they're the first to implement SLI, and support a handful of older games that use it exclusively. They're powerful cards. Using two of them in a pentium 1 system goes to waste however, as the P1's bus bottlenecks them. Yes, even in my P1 233 system.
I own such games that refuse to play [on any other 3dfx cards] but voodoo 2s with certain drivers!
Got lucky and picked up a Monster 3d II PCI (12 MB) on ebay Germany a couple of weeks ago for 1euro plus shipping. Included the SLI cable and external VGA cable.