The Sparrow is a light Loyalist Mech, equipped with Auxiliary and Turret weapons. While initially available as a training vehicle in the original tutorial, the tutorial was completely replaced and the Sparrow made fully pilotable in the Up-Armored Edition.
The Sparrow has barely enough armor to be called a mech, but then it's not usually deployed in the typical fashion. Stripping all but the front armor from the chassis allows it to pack some decent artillery and a plentiful magazine while retaining excellent mobility. Sparrow teams are unmatched in how quickly they get in, launch ordinance, and move on. Skilled drivers are even able to hop obstacles, just don't tell the engineers they're doing that.
Where Sparrow drivers are the real cowboys is when, en route to position they break through contested lines rather than go around. It's a proud tradition among their drivers to travel "as the Sparrow flies". You can tell seasoned drivers by the odd ski crouch they do when under fire. Even happens at parties when a loud noise goes off.