Me: Auto sniper? Snipers are people, not guns, you dumbfuck.
In the older verions of CS it was a more powerful gun (the G3, originally available to both teams) that flew under the radar despite people like me dominating with it to the point of disbelief and worship by opponents and teammates. Like the current auto snipers, the G3 was never accurate on the first shot which made shooting, retreating, and shooting again impossible.
When it was given increased accuracy, people started to complain about it. Then the accuracy was lowered again and another auto sniper was introduced and the two became team-specific.
It is often banned even when the 'AWP' isn't because people get frustrated when they are killed by an auto sniper, not because it is an uber gun like the AWP. The Scout is never banned, and is "silenced" which is why you can't hear it from a distance.
The auto snipers are more difficult to use than the regular snipers since you have to sit in the same spot and shoot very slowly to be accurate and can easily be killed by someone not in your scope or anyone with a regular sniper. Because of this it is rarely used and is only good under very specific conditions.