Grenade Gun
I wish we had a grenade gun.
Have it be a 6 shot weapon that does 50 damage. No auto shot setting. This makes it per an individual shot, better than the auto cannon but the auto cannon still has more overal firepower per a clip and a full fledge cannon still has a stronger explosive round, and just as many shots. Have it be lighter than either of those big weapons.
Initial starting ammo should be explosive, inciderary, and smoke. After you research stun bombs and alien grenades, add stun and alien grenade ammo.
This creates a weapon you will use for the whole game, but is distintly human.