Modernize Mordekaiser
(Be happy I didn't type Mordernize Mordernizer)
Make his Q a stun. The little split projectiles also Stun. Mord is very low mobility, if someone comes within melee range of him (or he can tactically use a minion to throw a stun out) he should be able to hinder them somewhat.
Renekton does this already basically, but he's highly mobile, so he should only stun 1 person. Riven is a good example of this as well, no one wants Riven nerfed, but how would giving Mord a stun make him so insanely OP that it's unallowable when Riven already basically has this.
Something like this:
Mace of Spades
Range: 600
**Cooldown: 10 / 9.5 / 9 / 8.5 / 8 (*.60 = 6 / 5.7 / 5.4 / 5.1 / 4.8) ** (full CDR on Morde would be somewhat awkward) Cost: 25 / 32 / 39 / 46 / 53 health
Active: Mordekaiser enhances his next attack, converting it to deal magic damage and replacing the base attack damage component with a base amount of damage. He swings his mace with such force that it stuns the target, and up to 3 additional nearby targets.
If the target is alone, the ability deals 65% more damage.
Magic Damage: 80 / 110 / 140 / 170 / 200 (+ 40% AP) (+ 100% Bonus AD) Single Target Magic Damage: 132 / 181.5 / 231 / 280.5 / 330 (+ 66% AP) (+ 165% Bonus AD) **Stun Duration: .75 / 1 / 1.25 / 1.5 / 1.75 seconds **