Sniper has probably the worst secondary weapon in the game (machine pistol is worthless), but his melee's pretty good.
As a sniper, I tend to hang out in view of friendly sentries - no spy in his right mind would attack you first, and as soon as I hear the engineer complaining about spies, I unzoom and bring out the ol' chop-chop.
My mouse also lets me dial down the sensitivity, which is great for zoomed shots.
Threaded Mode