in northamerica (canada and the united states) their are Ford and Dodge police cars with some places still having some older Chev police cars. Other parts of the world use different makes - i.e volve,fiat, seat, audi and on and on.
Give us a year and a country, and I'm sure we can help you out better. Police cars currently in use by the O.P.P. -Dodge Charger -Ford Crown Victoria - Ford and Chev SUVs Some of the forces are still using Chev Impalas... but it's rare, Haven't seen one in a while... or in certain cases, we have a police force around here who have a Honda Element, and a VW Bettle as police cars... But they generally don't scare off the speeders too much ;)
I agree with Chris. I will add this though. It also depends upon what the budget allows that can be purchased inexpensively and in great volume. With the current problems in Detroit, I'd not be surprised to see a LOT of foreign countries getting deals on fleets of USA produced cop cars.
Crown Victoria's and the older Chevrolet Caprice's were always designed as fleet cars anyway, for use by police and as Taxi's Personal opinion, I think Crown Vics make beautiful police cars... square or round... and From the stats I've heard (Although I don't remember where) they aren't the fastest or have the best handling, but they make good Balance of all these things and that's why the police prefer using them over all the other options. The Gas Milage on them isn't terrible either. I do like the fact that they've started using Chargers though... They Make a real smart looking cop car... especially now that the O.P.P. has gone back to using black and white cars.