It's Spartan Laser: Low Calorie edition. Sucks against vehicles but is handy for anti-personnel compared to the laser since unlike the laser, the rail gun is at full power a few seconds before it forces you to fire, meaning you have a larger window to line up a shot and you also have a higher potential rate of fire. The down side is the projectile is not quite so instantaneous as the laser, and that it's worthless versus armor.
Personally I like it, especially on the Spartan Ops missions where it has infinite ammo.
It's not completely worthless against armor, takes 6 shots against a Scorpion or Wraith, so while it might not rape one like the Splaser can, it's much harder to defend against at the cost of overall power. Pretty much 1-2 more people helping and it's highly likely you'll destroy the vehicle. It's more of a Jack of All Trades power weapon, at the very least it's great at assisting a vehicle kill.
Yeah same here. One of the few power weapons I really like. I think it actually fires faster than the rocket launcher, plus you really don't have to worry about splash damage in close quarters. The only downside IMO is there is no way to cancel the shot while its powering up.
there is this thing called YY that has been used since the dawn of halo
Not completely worthless, but most of the starting weapons will be better for destroying vehicles. The railgun is an AP weapon through and through.
Not really. The Railgun does damage to vehicles much faster than any of the starting weapons do. DMR has proven to be the fastest so far and it'll take ~30 seconds of constant firing, no shots missing to destroy a Mantis. Takes ~17 seconds to do the same with the Railgun.