I try not to use it too often, but it's fun and very useful for safe leveling of troops as well as getting map loot:
[Works best if the enemy is an archer or psy, but works with melee units too]
When you're down to the last enemy of the map , surround the enemy completely (either with 4 units or 3 units and an obstacle) and proceed to do the following:
Step 1)Have your units Shove the enemy for exp, and/or have one unit attack them with a weak weapon (Exp for fighting/shoving)
Step 2)When the enemy gets to low health, use Mind Shield to heal them back up (Exp for healing)
Step 3)When the unit the enemy is attacking gets to low-ish health, use Mind Shield to heal them
Step 4)On alternating turns, Rest, to regain the energy for Mind Shield.
Step 5)Repeat, and continue to be a troll to the poor last enemy
Step 6)This strategy of surrounding/healing/resting also allows you unlimited time on any map to secure any loot you missed :)
[Exp Farming Intensifies]
I'm not sure if it's been changed or not, but it used to be that an enemy won't attack a unit with a counter-attack that would kill it. In this way you could corner an enemy with counter-attacking characters and hold it hostage until you decide you're done.
It seems like that part wasn't changed yet, since they'd only my non-counterattack units when doing this, but I haven't had the chance to test it with all counter-attack units. A work-around to this still, is simply un-equipping the weapons from those units and they will be attacked too. It's better if it fights back anyways, since you then get exp for healing your units back up.