1st choice: Geforce 6800GS. It is getting increasing harder to find this card for under $200 in AGP interface, but it's most likely the best for gaming @ the $200-$250 price point right now.
Academic Superstore has it for $189 before shipping. You might have to be a student or teacher to be eligible for the price, not sure.
2nd choice:
Radeon X800 GTO $193. 12 pipelines, 256-bit memory bus, high clockspeeds, good overclockers. Great for the price.
3rd choice: Radeon X800 GT. $100-150.
4th choice: Geforce 6600 GT. $120-$150.