In the beta, I believe there's 4 weapons, which can upgraded 3 times each. Weapons are upgraded by driving through another weapon pick-up, so it becomes a chose of whether you'll use your level 1 weapon right away, or whether you'll save it and upgrade it to a level 2 (or even 3) one.
Missile:
1 - Single missile, no heat seeking.
2 - Two missiles, heat seeking (I think)
3 - Swarm missiles, heat seeking.
Electric:
1 - Single electric jab, straight ahead. Delays enemy.
2 - Electric jab that targets a player (I think).
3 - Thunder bolts rain from the sky.
Pulse:
1 - Emits a short ranged pulse from you, delaying any enemies nearby.
2 - Throws a ball forwards, which explodes into 3 (I think) pulses.
3 - Tornado.
Speed boost:
1 - Short speed boost.
2 - Longer speed boost.
3 - Shoots a portal up ahead, which will teleport you further up the track.
Each weapon can also be thrown backwards. They have a different effect, based on either which weapon you have or how upgraded it is (not sure which) - some explode instantly, others lay there as a mine, etc.
In addition to this, you also have your boost meter (which is built up by doing big jumps, skidding around corners, and stuff), which can be spent on a side slam (which will hurt and delay the person you hit) a shield, or a short speed boost.
That's just in the beta. Think there may be more in the full game, but I'm not sure.
