Cannonball's never met a problem he couldn't blast, drill, or shoot his way out of, and it shows. He's mastered the strangest weaponry he can get his hands on, and his latest find is a pile of HERC gear straight out of Umoja, which he enjoys immensely. During his time as a mercenary, he became close friends with James "Sirius" Sykes, and the two rely on one another for their bigger jobs.
Cannonball is a heroic HERC outlaw available for Tychus Findlay in Co-op Missions. He is a beefy part of Tychus's "muscle" that can use Heavy Impact to close ground, and has upgradable gear that allows him to stay in the fight and soak enemy fire for long periods of time.
Particularly, he excels against enemy compositions that either require vast amounts of firepower to chew through (such as Infested Terran swarms on Dead of Night or Miner Evacuation), or lockdown of high-value targets (such as Amon compositions involving Siege Tanks). His weapon deals the same high rate of damage regardless of armor type, particularly once Redline Fuel Cells are unlocked, turning him into a DPS powerhouse in sustained fights (again, Dead of Night or Miner Evacuation.) He is completely useless against enemy air units, as are Tychus' other Muscle heroes, so a hero strong against air (Sirius with Thunderbolt Missiles, or Vega with Psi Projector) is recommended in missions where Amon's compositions involve more than one air unit.
His ability to dash forwards can put him well outside the safe healing range of Lt. Nikara, the almost completely negligible damage of Heavy Impact, and the long charge-up time for Redline Cells means he's very capable of getting himself into situations he can't get himself out of--thus the usefulness of the Critical Response System. Also working against him is his tendency to massively overkill targets with an extremely high damage output in a single shot--even worse after MALICE ammunition is researched. This special ammunition has the potential to deal enough damage in one shot to kill a Colossus or Archon instantly, but may also simply tie itself up swatting Zerglings with literally ten times overkill damage. Tychus' Marauder, Rattlesnake, is on paper much more suited for damage output thanks to his Stimpacks and Revitalizers increasing attack speed combined with an area-damage slowing autoattacks (after Hammer Munitions is unlocked). Most boss enemies are Armored, so Rattlesnake's weapon will do full damage (not to mention that Revitalizers can provide a staggering damage boost to all friendly units). Rattlesnake's damage may be halved against units like Zerglings, but the area damage will make short work of their small health pools regardless. The same remains true for Infested Terrans on the aforementioned missions. He is best used to counter Amon's Siege Tanks, as he quite simply eats them for breakfast, but Blaze's Oil Spill is a reliable choice to cut a Tank's damage output by three quarters, while Oil Spill is still extremely useful (and more highly-damaging) against enemy targets of all types and Heavy Impact has questionable value versus many of them. Rattlesnake's area damage and anti-armor quality also means he can chew through Siege Tank lines effortlessly while keeping your armies alive from the Tank barrage with area healing Revitalizers.
Cannonball remains an excellent, if outclassed choice for your primary tank. His Critical Response System allows him to shine if you are for some reason neglecting Lt. Nikara.
In early builds of Tychus's Outlaws in Co-op Missions, Cannonball was based around the warrior class from World of Warcraft. He uses the remnants of a cut mechanic for Tychus named "coldheart," where all of Tychus's units would gain attack power and speed the longer they were in combat.