Here's what I've got for the Tactics skill in my homebrewed d20 system. it is based primarily off of Star Wars Saga Edition...
[sblock=The Tactics Skill]Tactics (Wis)
The tactics skill represents your knowledge of combat tactics and is used primarily to gain advantage or to grant advantage to your allies in combat.
Aid Attack: In combat, you can aid another character's attack by forcing an opponent to avoid your own attacks, making it more difficult for him to avoid your ally. You may use this action whenever one of your allies makes an attack against an opponent that you could also attack. Make a Tactics check versus a DC of 10. If successful, you grant your ally a +1 bonus to his attack roll against that opponent. For every 5 points by which your check result exceeds DC 10, you grant an additional +1 bonus to your ally's attack roll. You must declare your intention to use the Aid Attack action after the attack has been declared, but before it has been resolved. When you use the Aid Attack action, you forgo 1 Swift action on your next turn.
Aid Defense: In combat, you can aid another character's defense by forcing an opponent to avoid your attacks, making it more difficult for him to concentrate on your ally. You may use this action whenever one of your allies is attacked by an opponent that you could attack. Make a Tactics check vs a DC of 10. If successful, you grant your ally a +1 bonus to his Armor Class against that attack. For every 5 points by which your check result exceeds DC 10, you grant an additional +1 bonus to your ally's Armor Class. You must declare your intention to use the Aid Defense action after the attack has been declared, but before it has been resolved. When you use the Aid Defense action, you forgo 1 Swift action on your next turn.
Assess Opponent (trained only): You may attempt to 'size up' an opponent's capabilities. As a Swift action, select an opponent within 12 squares to which you have line of sight. Make a Tactics check, opposed by a Deception check made by your opponent. If your check result equals or exceeds your opponent's check result, you learn one of the following: your opponent's highest attack bonus, your opponent's total Damage Reduction, your opponent's Fortitude Defense, your opponent's Reflex Defense, or your opponent's Will Defense.
Expert Knowledge (trained only): You can make knowledge checks related to military studies with a DC higher than 15.
Locate Sniper Position (trained only): You can make a Tactics check to oppose an opponent's Stealth check to remain hidden after making a ranged attack from concealment. You do not suffer the penalties due to range that you suffer on a Notice check.
Military Lore: You can attempt to recall useful lore about any specific Military unit that you encounter.
Predict Behavior: You can attempt to predict you opponent's next action. Make a Tactics check as a Standard action, opposed by a Tactics check made by your opponent. If your check result equals or exceeds that of your opponent, you may force that opponent to re-roll one attack or check that he makes before the beginning of your next turn.
Sniping (trained only): If you make a ranged attack against an opponent that can't pinpoint your location, you can deal extra damage. Make a Tactics check as a Free action vs DC 10. With success, you deal an extra 1d6 points of damage on your next attack. For every 5 points by which your check result exceeds 10, you deal an additional 1d6 points of damage.
Suppress Enemy: In combat, you can distract or interfere with an opponent, making his attacks more difficult. As a Standard action, select an opponent against which you could make an attack and make a Tactics check versus a DC of 10. If you succeed, that opponent takes a -1 penalty on its next attack roll or skill check. For every 5 points by which your check result exceeds DC 10, your opponent takes an additional -1 penalty to his next attack roll or skill check.
Total Defense: You can defend yourself as a Standard action. Make a Tactics check. You may replace your Reflex Defense with the check result until the beginning of your next turn. If you choose not to take any attacks of opportunity until the beginning of your next turn, you gain a +4 bonus on your skill check.[/sblock]
