Also depends on what you need: Drivetrain, class, power limit, etc.
Good potential used stuff:
Demios (Avoid the '97 LX, though)
Mazda Protégés
Silvia K's (avoid the Q's unless you want a lack-of-power challenge)
any old 80's car ('83 or 90' RX-7, Skyline RS-X '84, MR2 '86)
Some of the FR-drivetrain Skylines (GT-Rs weigh more, anyway)
Supra '93
Of course, you could make yourself go nuts and try to use a new car:
Daihatsu Mira (best of the new cars <10k Cr.)
Daihatsu Midget
Ford Ka (Hmmm, is this under 10k?)
Fiat 500R