Large aliens are toast from the knockback.
For me, chainguns are by far easier to eliminate rather than the Pulse Rifle. The Pulse Rifle's knockback, IMO is far greater and I can hardly ever kill a moderately experienced Pulse Rifle. Maybe I just suck... but hey, I try.
If you know how to use the Pulse, you're untouchable. Same with the Chaingun.
My favorite human weapon though is the MD, mainly because it requires a lot practice to get a hold of, and I appreciate its damage per round. My second would be the shotgun. Third being the lasgun and on down. I only use those three weapons for 90 percent of my playing, the rest are for base elimination.