Java is nice for cross-platform devlopment.
Though it is a bit slow. It is difficult doing complicated things in Java, but that may be my inexperience...
Delphi (object Pascal) is a nice proramming environment. Also doesn't create fast executables, but it can do nice things. Delphi for simple tasks has a short development time IMHO.
C++ is the mother of them all. While not easy to learn, it allows you to do just about everything that your machine is capable of. Creates the fastest executables but has the steepest learning curve and the longest development time.
They are all OO so any of them would do.
If you are really up for a challenge: amanda
It is an interpreter for a functional language (as opposed to object oriented). Real pain in the rear to get used to; quite fun to show friends and see them baffled at your program
edit: too many changes to note here 