Being the first one here, I recommend:
4x4: Toyota Prado or Mitsubishi Pajero or Nissan Pathfinder
Sedan: Cheap - Honda Accord or Mazda 6
Sedan: Not so cheap - Lexus LS 400 or BMW 5 series
Remember in UAE....best 2nd hand value is Japanese, then European and then US vehicles. Toyota is always a good bet here.
If you want to pick up cheap good cars that have fallen down a lot, then look at Alfa Romeo, Ford and big-ass BMW and Mercedes....you get a lot of car for your money!
Hey..these are my suggestions....always do your research before you buy!