The ones that I have so far tried that can be purchased and would recommend for goofing about in are:
Lancia Stratos, as previously mentioned. Bog standard, on N1s or N2s, will drift all day whether you want to or not... to start a slide, just turn the wheel. It's controllable, too. The Protomotors Spirra will power oversteer beautifully on N2s, and with an exhaust and chip is about perfect. Feels a bit clumsy and heavy next to the Stratos but its long wheelbase means things happen gradually. A real pleasure.
The Supra RZ is also nice to slide.
If you want a real challenge though, try a secondhand Clio V6 (with oil change) on N1s. It's more difficult to drift than the other two MRs I've mentioned, but once you get it into a drift it combines the Statos's agility with the Spirra's adjustability. It makes the Stratos feel too easy and makes the Spirra feel soft and heavy.
If you like oversteer, I wouldn't recommend an AC Cobra. In my hands at least, it's got too much understeer. Dunno if the Shelby version is any different. Also, the Carlton is a nice sideways tool but its lack of power off boost (in standard tune) makes it hard to drift around slow hairpins where 1st gear is too low and 2nd gear is off boost.
