Swann - I really liked the Drakken Laser Drill in that WoL campaign mission. Here, Swann also has Factory units and Goliaths in particular, which he specializes in. He’s also adept at tower play
Karax - Tower play, but I like having SoA lasers as part of his core game play. Just “zapping stuff” is fun, and a novel ability to play! His support abilities are nice, and it’s great to have him as an ally. Mind Control from Energizers can be really strong.
Also, all 3 of his prestiges are viable. Something for everyone! Even his P0 is solid, if you don’t want to level him up
Stukov - I dig infested Terran theme, which is his shtick. Infested walkers from ICC, Rax, and Bunkers are all fun and unique to work with. Infested Diamondbacks are such a joy to use.
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Fenix - Champions really are powerful with high DPS. Plus, I liked using Scouts in Sc1. More so than Carriers!
HH - Strike Fighter Platforms are fun to use! Ditto with Mag Mines! Like a variation of the laser drill or Orbital Strikes. Air units are elite units, but his ground units are fun too, with Hellions being actually different vs. its Hellbat variation!
Stetmann - Stetalites are a unique support ability. P2 Super Gary is fun to just obliterate a lot of things, while managing his (-). P1 is fun if you find using Super Gary for everything boring, and lets his units shine more
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Raynor - He has not detector unit which is scary! However, Com Scan is the only way to gain vision and detection, safely. Sure, HH can use a SFP for vision, then plot down a Raven. But the Raven will likely die if it’s in enemy territory, or u just wasted a Strike Fighter charge. Mass infantry is always a classic, which Raynor specializes in. Here, he can do the famous MMM bioball! Firebats are nice to tank and vs. anti-swarmy
Abathur - Toxic Nests are fun to plop down. For extra creep, vision, in addition to damaging ground targets and extra bm. UE are bloody powerful. I’ve always liked using Guards and Devourers from Sc1 BW, so neat they made a return here!
Alarak - He’s got the typical Protoss repitoire, but centered around a hero unit that’s literally the mainstay of this CO! It’s fun on his P2 to invoke those bursts of power as needed. P3, MoShip is in overdrive, providing a truly unique air force!