deends on the sport, sorry. you need diffrent parts of your body for diffrent sports.
but every sport needs conditioning.

plyometrics and flexibility training is great conditioning for all sports.

get a personal trainer and if not run and eat healthy limit your junk food

Agree with the plyo's, flexibility, but let me add core training and interval training. You cannot beat either one and whatever sport you play, you will notice a difference in quickness, speed, vertical, power etc if you train the core and train it correctly :)
Good Luck Alex!

Here is an article on Core Training:
http://tinyurl.com/c9vg2z

And here is an article on Interval Training:
http://tinyurl.com/ybg3cec

Enjoy and hope it helps a bit :)

Running always works, or biking. Just look at Neil Armstrong, he beat cancer by biking.
Plyometrics is also a VERY good workout.