it has to be added to the skills your champ already has but here is one i thought of and had a good chuckle but what if 
's w also gave half of the effect of the unique passives he has on him like half of the 
reflect half of the damage burn from 
and half of the crit reduction from 
Cho'gath's ult cooldown resets if it kills a unit.
can crit for 1.3k from a mile away on an invisible trap.
wait a second .....
Q can keep bouncing to targets behind the previous one, a single crit translating to all future bounces.
Can keep ult resetting as many times as she can press R during the time that the Q passive is on them
No change
gains 50% tenacity while ulted
W can crit :^)
Q:
W:
R:
to be honest, just the fisrt one would break him, but I fell the need to make Gnar a very dangerous main line power outlet. humm... I would be happy if riot made:
W: now scale with 220% of AP. R: now scale with 60% of AP.
I would show people how 220 volts per 60 hertz is better.
Ultimate no longer has a maximum duration and can be channeled until Janna moves or is CC'd.
No Worked Ground
INFINITE BARRELS
Ult is completely global
W CD is reduced nevery time you block an autoattack
passive refreshes on minions
ultimate can turn on a dime.
Each second spent in his poison trail (Q) reduces the effect of all your items permanently by 0,5%.
So if you spent a total time of 200 seconds in his poison, all your items are worthless. :)
R slow immunity extends to damage portion of the slow abilities (old bug with old yi, you buying 
made him immune to every single of your damage abilities)
Gains 1% crit for every point of lethality.
If both of Q's beams hits an enemy champion it is a stun and also increases damage of auto-attacks.
Passive cooldown reduction now works on his ult and CDR no longer reduces the amount of reduction his passive gives.
E is now a passive "turn on and off" thing.
w cd gets reset if someone dies under his charm
Rework was reverted. (Get it? because the rework was horrible.)'
Turn his %hp scaling dmg back into his w and make it also scale with HIS hp. Or give him back his old ult.
auto kill below 20/30/40% hp
refunds 20% cooldown per kill
Ult now scales on AD
Ult also fears nearby enemy champions on kill, not just minions. AoE damage from tiamat/hydra items can apply bleed stacks. Stacking on a super minion or monster can apply Noxian Might at 5 stacks.
Combine current and old passive (I.E. current passive, plus for every stack your autos inflict 1.25% current HP physical). Gains range for every 2 stacks instead of 4.
W now has infinite base damage, has a 1 second cooldown at all ranks, cost no mana and has 600 range.
