Right now I only have the standard set(front-mounted machinge gunes and rear-mounted mines), and the melee set(front-mounted shot gun and rear-mounted grenade launcher). Post your favorite weapon combinations here!

assault (machine guns front and mines back)

I've unlocked the first 3 sets now. I still like the Missiles, especially the lvl 3 missiles, they're heat seaking!

we should be able to create our own weapon sets

Assault is the best for me, but I like the Tank Cannon/Rear Shotgun occasionally as it's nice to have a rear weapon that's actually decent.

Having un-locked them all, I'd say my
favorite is Ravager (only class A cars).
It has, if I remember correctly, the
multi-rocket pod in front, and land
mines in the rear. If I'm expecting
heavy attacks from behind, I set the
mines to level 3. If I think I'll need
to aim the multi-rocket pod yet would
still need rear support, I set them to
level 2. Finally, if I need a lot of
wreck points I set the pod to level 3.

As you can see, one can use it for many
scenarios, but unfortunately it's only
for class A cars.