Definately the Voodoo3
It's got pretty good 2D and decent 3D speed in Glide, D3D and OpenGL.
Try and step up to a GeForce 2MX, but if he can't afford it, then the V3. Don't bother with anything based on Savage3D (or S4 for that matter).
Seriously, 3dfx and nVidia are the only companies you should really consider for a Video card. ATi's Radeon is pretty good...but their Driver support has yet to be proven. With the release of the Turbo GL drivers, Matrox can finally keep up with the V3 and TNT2, but for about 2x the price...Matrox has other things going for them, but unless you want something specific from a matrox card, they are a very expensive choice compared to nVidia and 3dfx (at the same power level of course).
S3 is kind of a joke. I can't believe Via actually bought their graphics division, they might as well have bought Trident