If you plan on using sniper rifles, you may want to stick with pistols until you can level up sniper rifles. With a fully leveled sniper rifle talent, and crouching, the sniper rifle’s reticule becomes the size of a shotgun’s, and can even be used in extremely close quarters situations the same way. Sniper Rifles unlock the Assassination ability, which makes the next shot extremely powerful while reducing the bob of your scope to nothing. They are slow firing, powerful long-range weapons. Sniper Rifles can be improved by Infiltrators and Soldiers.
This can be used to take down tough enemies, or enemies that are outside of the shotgun’s effective range. Carnage makes your next shot an extremely powerful projectile that travels in a straight line. As you probably suspect, Shotguns are good for close range, and putting points into the Shotguns talent will unlock the Carnage ability. Shotguns can be improved by the Soldier and the Vanguard. Marksman gives you extra damage and fire rate while reducing your heat build-up for a short period. They are powerful, midrange weapons, and they unlock the Marksman ability. Pistols can be improved by any class, and should not be dismissed as a weapon-type. If you fire too frequently without letting your weapon cooldown, it will overheat, and you will be unable to fire for a while. Each class can carry around one of each weapon type, but a class’ proficiency with a weapon can be severely hampered by not having any points put towards that weapon. There are four weapon types in Mass Effect. If you don’t have any training in a weapon type, then your damage and accuracy with that weapon will be hampered.
Which one is the most fun, or the best for a first playthrough? If you look for an answer for this question on most forums, the response you usually get is either Soldier or Vanguard, with people often decrying the other four classes. So there are some people out there who are new to Mass Effect, and don’t know anything about the classes.