No loss, no kite, no luck, impossible mage

[MaroonMaurader]

Fun with Sacrifice infinite combos!
1. Sacrifice + infinite mana combo + repair droids = infinite resurrection for any unit in your army.
2. IIRC, you can also sacrifice the bears druids summon, which they can do every 2 turns.
3. Low-intelligence hero + Tirex (or other tank) + Sacrifice + Heal + infinite mana
4. High Astral-Damage resistance + tank + Sacrifice + Heal + infinite mana (astral damage resist lowers damage from Sacrifice, but not amount of healing given).

Fun with Turn Back Time!
1. Turn Back Time + Inquisitors (or any other resurrecting unit) + infinite mana lets you reuse their resurrect.
2. Turn Back Time + Sacrifice + infinite mana.
3. Target on turn 1 of a battle; turn back time on turn 2. If your initiative checks are just right, you can even do target, then turn back time at the end of T1, and repeat that on T2 etc. Very mana-expensive, but it can buy you several turns before you start actually taking losses.

The Undead!
Eviln is a very powerful spell in the right hands. There are whole articles on this forum devoted just to the solo Black Knight + eviln strategy, although you're free to add in other units if you want.

Depending on the artifacts you have, Troll-at-night strategies can be extremely powerful. Troll regen + Stoneskin + Divine Armor + artifacts giving physical resistance can quickly give you a tank that ignores all physical damage. Add in Target to make enemy units shoot at them, and you've got yourself a game-breaker for the first 2/3 of the game. Eventually enemy stacks will start doing more than 700 damage in a turn, at which point it becomes far less useful.

I've heard good things about Royal Thorns, but haven't really tried them out myself.