There's no contest here. You could — and everyone did — snipe other players across the largest Halo maps with the pistol from Halo: Combat Evolved. If you played Blood Gulch, you were sniped by a pistol. And you sniped with the pistol.
It was just how things worked.
The pistol's power came from a near-complete lack of recoil and little if any damage falloff. Add in semi-automatic fire and a low time to kill and a healthy store of ammo, and you've got yourself a killing machine without peer.