Warwick is the best on attack stacker hands down. 1 ult can take out most anyone tank or not.

I do this with teemo with full atk speed runes. I get wits end, malady, razor, mallet, mercs and gunblade or abyssal. Teemo would be better against rammus because you can throw down a shroom as hes powerballing toward you and he hits/knocks it up with you still safely behind it. The fact that you can buff your attack speed with stealth also majorly helps you gank. Just stand on/near a shroom while stealthed and wait for somebody to walk over it.
Good thing about this build is that you can end up with a lot of mr and a little armor that can be subsidised with a well timed blinding dart.

Koggy is the king of on-hit effects since he opts for maxed out AS.

According to the learning center (which isn't always right around update time, but is eventually), the spellvamp is around 25% -- probably because if you want to stack gunblades and can, the game is already logistically over one way or another. May be viable for some, but that's some serious gold right there, no?

No one's said it so I'll say it...Twitch. His ulti can nail several champs at once applying the on-hit effects to all of them. Twitch beats out Kog'maw in this one instance.

Ive said it already.

As far as teemo, His stealth dosent compare to twitch's, But his mushrooms can make up for it

Kog'Maw, I only see his q as usefull on an onhit champ since if loweres armor but otherwise not really an On Hit champ

WarWick, is a very understandable On Hit champ for hit ulti and his E. so if they try to get away they cant,

Akali is another good on hit champ since she has the highest base Attack Speed of all cahmps ATM. she can reach the cap rather quickly.

Ashe, with her Q is a nice on hit as well

Baseically any DPS can become an on hit CHamp it all depends on play style.

I personaly prefur twitch and his poison passive, You may prefur Ashe slow on hit ability or Warwick and his ult with his speed boost ability

Most of you are neglecting an important factor - these items add MASSIVE IAS, and a champ like WW or Twitch will cap out before you finish the build, meaning you're just not getting full value from your purchases any more.

Bloodrazor + Malady + Mallet + defensive items will serve most champs very well, with champs like Teemo or Kog having room for a third IAS item.

teemo poison on-hit

The Hextech Revolver's Spellvamp is now unique, Hextech Gunblade is NOT unique (in the tooltip anywhoo).

twisted fate..come on guys haha