HARK VS. HARK
Most Lethal Combo::
Saws, Sards, Infantry, Occasional Flame Tank
In General: When playing Hark Vs. Hark you want to basically make 4 units: Buzzsaws, Infantry, Sards (regular), and an occasional flame tank (maybe 1 flamer for every 10 saws). If your enemy is not making as much infantry and making more saws than infantry, then make 3 assault tanks for every 10 saws. When you attack the harkonnen hoarde with your hoarde, do 2 things: #1) use ctrl+shift (attack move) and target behind your enemy. #2) drop a harvester in front of your army as a distraction to the enemy.
Should I be Missle Tanks? NO. only unless you need some to protect your base from gunships (long game).
Should I be Making Catapult? Possibly.. An occassional catapult is a great thing to place behind your front line and fire at an enemy rock loaded with infantry.
Should I be Making Gunships? If money affords, most certainly you can. But do not do it if it sacrifices potential ground units.