The MechWarrior video game franchise is a series of sci-fi simulator games where the player can take command of gigantic humanoid war machines and take the fight to their enemies. These are BattleMechs, or 'Mechs for short, and some are much bigger than others. Small 'Mechs have their own role to play, even if they look puny compared to assault-class chassis like the Atlas.
In every MechWarrior game (and in the lore), small 'Mechs are at the low end of the weight spectrum, weighing anywhere from 20 to 35 tons. These tiny 'Mechs can do what their larger cousins cannot, and in lore terms, they are much cheaper to build and field too.
The Combat Role of Light 'Mechs
Every 'Mech needs a clearly defined combat role, and most light 'Mechs fulfill roles such as scouting, raiding and capturing targets. In the lore and in the computer games, light 'Mechs take advantage of their small size and superior speed to race around the battlefield, outmaneuvering the enemy's tanks and larger 'Mechs and taking them by surprise. Light 'Mechs don't hit hard, but they often hit first from unexpected (and critical) angles. They're like wasps, darting around and stinging the enemy while taking little return fire, especially when they make good use of terrain or their jump jets.
These 'Mech are often used for scouting, even though they can't fly like VTOLs can. Light 'Mechs can run across the battlefield to spot the enemy's location and assets, then report back so the team can figure out what to do next. In MechWarrior Online, a 12-player team may include a few light 'Mechs, and their players can race ahead to find out what the enemy team is up to. Once a player spots the enemy, they can put that enemy on the team's radar, and 'Mechs that carry LRM launchers can perform indirect fire support and damage the enemy, all while the light 'Mech is acting as a spotter. The same is true for calling down airstrikes in that game.
MWO's objective-based game modes call for capturing certain "king of the hill" locations. Big 'Mechs can certainly blow up the enemy, but they may be too slow to capture those points. Light 'Mechs, by contrast, can run off and capture (or recapture) those points before the enemy team racks up enough points, and often, this will decide an entire match. No other class of 'Mech could pull this off.
Finally, light 'Mechs might act as surgical strike platforms, though the same is true of medium 'Mechs. A BattleMech isn't a solid unit with a single hit point bar; a 'Mech is made up of many bodily locations and weapons, and it can get broken up piece by piece. If a bigger 'Mech badly damages the enemy and blows off their armor, a light 'Mech can run in and pelt the enemy with persistent fire and focus on vulnerable arms or legs. This can neutralize the enemy as a threat, and the light 'Mech probably won't take much return fire, especially if they attack the enemy from behind. Plus, with their speed, light 'Mechs can hurry to any key spot on the battlefield and perform a surgical strike on demand.
Common Light 'Mech Weapons & Chassis
All of the computer games include a variety of light 'Mech chassis, from a few in MechWarrior 2 and MechWarrior 3 to MWO's much larger roster of light 'Mechs. One common light chassis is the Commando, which is actually a bit slow for a light 'Mech. In return, this machine is armed with an SRM 4 and SRM 6 launcher for a serious close-range missile assault on unsuspecting opponents. A single medium laser is added to the chassis for ammo-free firepower.
Meanwhile, the beloved Jenner chassis focuses on laser weapons instead, having two medium lasers per arm and an SRM 4 rack on its torso. The Jenner is a quick machine that can perform hit-and-run attacks on larger enemies and deal surgical strikes to blow off a huge 'Mech's damaged arm or take out a leg.
Meanwhile, the Clans have some light 'Mechs to offer as well, with the KitFox/Uller being a staple. It's a bit underwhelming in MWO, but it does enjoy a range advantage, being able to whittle down the enemy from afar while having average speed. There's also the popular Mist Lynx, a 25-tonner that features astonishing sped and more firepower than Inner Sphere 'Mechs of a similar weight.
Rarely do light 'Mechs use any ballistic weapons, since those tend to be big and heavy. Instead, light 'Mechs use a handful of small, light weapons, with small and medium lasers being popular choices, along with SRM launchers or LRM 5 or LRM 10 launchers for fire support. Some light 'Mechs might even be outfitted with many machine guns at once for a low-heat, close-range beatdown. Combined, these machine guns do a lot of damage, and they can easily destroy the internal components of a badly damaged enemy. Light 'Mechs equipped with a handful of machine guns are effective finishers.