Ideas for Twitch

As a plague rat, he should spread disease far and wide.

Also, he is just weak right now, and we know riot wont revert the change that made him weak (the Q timer), so lets get imaginative.

W Venom cask Enemies in a target area take 20/30/40/50/60 (+.1 AD) physical damage, are slowed by 25/30/35/40/45% for 3 seconds, and are afflicted with 2 stacks of deadly venom.

E Expunge (IT WILL NEVER BE CONTAMINATE!!!!!! NEVER!!!!!) passive: If an enemy with stacks of deadly venom dies, nearby enemies take 0.5/1/1.5/2/2.5% the killed enemy's max hp for each stack of deadly venom that was on them. Epic monsters cause 1/3 damage. Champions may not take more than 20% their maximum health from this (In case of Mundo) active: All enemy units with stacks of deadly venom on them take 20/35/50/65/80 physical damage plus 15/20/25/30/35 (+.2AP)(+.25 bonus AD) per stack of deadly venom on the target. Additionally, these enemies spread deadly venom to other nearby units.

tl;dr Base damage on W and E makes units that twitch helps to kill explode in poison-y glory, as well as spreads poison on cast.