For a good value Shiraz try Wyndham Estate Bin 555 - frequently on special in one of the supermarkets for around $12.
Our favorite Sav Blancs are Wither Hills, Lawson Dry Hills, Jackson Estate and Saints. All Marlboro (of course) and all to be had for less than $16 if you keep your eyes peeled, watch the supermarket flyers and pounce whenever they're on special.
Unfortunately on a wine tasting I was tempted to try decent Pinots from Central Otago and find it very difficult to drink stuff from elsewhere now (even reasonably pricey stuff). DON'T try Peregrine (approx $35) or you won't want to drink any other Pinot...