The Starcraft Card game
Air and ground troop classifications

Why:
So you know which cards are air troops and which are ground so you can attack with the right attacks.

Ground
The following units are all ground types:
All buildings (even while moving).
Zealot
Probe
Dragoon
High Templar
Reaver
Archon
Drone
Zergling
Hydralisk
Ultralisk
Defiler
Infested Terran
SCV
Marine
Firebat
Ghost
Vulture
Seige tank (Seige or tank mode)
Goliath

Air
The following units are all air type:
Shuttle
Observer
Scout
Carrier
Arbiter
Overlord
Mutalisk
Queen
Guardian
Wraith
Dropship
Science Vessel
Battlecruser