240Sx is a great all around car with a zillion parts available and cheap to own/maintain. You can also pick your body style/appearance, all the fundamentals are basically the same (I went S14 because I like newer interiors). Lots of options for power, LSDS, suspension, fit pretty big wheels/tires, etc etc. The E30 is a cool choice too, but it is a BMW, so some things will cost more. Miata is another nice fun RWD car with lots of available parts, the small size of wheels, tires, brakes, etc helps keep costs down. For AWD I really like the old 2.5RS, but they need a lot of stuff done to be pretty fast, and cost way more than $3k. For $3k, I say look for a lightly modded 240SX or maybe E30 (not sure exactly what they/parts cost).