Ryze - Shown by OP. Ultimate can be recast before even half of the duration has expired. If his W is spammed rapidly enough, the animation/spell effect vanishes from the target. Permanent snare is easily possible.

Pantheon - Does not proc his passive.

Udyr - Works with his passive.

Sona - Weird weird effect. It seems powerchord works off 2 buffs; the buff that makes the next attack a powerchord, and the buff that chooses the 'flavour' or type. If there's no buff determining what the next spell is (eg, you have the passive up but no spell levelled, or you just consumed the last one), she resets her auto timer, and just auto attacks above the attack speed cap. I counted 20 auto attacks in about 6 seconds at one point. Must be a reset glitch. A macro is required for this.

Maokai - Hilarious effect. Since the shield can't be activated if it takes any damage, it's best to have an ally (or enemy in my case) do the shield macro for you. Maokai hit 2.0 attack speed, and still had his passive up for every single auto attack. And proceeded to duke it out with tibbers, gaining 100 hp per auto.

Annie - Does not proc her passive.

Malzahar - Bitterly disappointed. Does not spawn voidlings :'(

Kassadin - Instantly fills his Force Pulse stacks, but the cooldown cap means it isn't a particularly spectacular effect.

Items:

Guardian Horn - Works off enemies using the glitch. Can be cast before the duration expires, for a permanent buff. Absolutely hilarious when used in tandem with a Ryze ult spam.

Guinsoo's Rageblade - Instantly fills the stack count, and will maintain it as long as you continue activating.

Tears (and associates) - Will stack them as expected. Kinda like leaving Amumu's W on permanently.