honestly i'd have to say cait is the best harasser in the game. Her gigantic range allows her to auto attack harass as well as her piltover peacemaker, which has even more range.. able to deal damage without taking it.

Yorick

Sorry this thread is a bit old, but seriously guys, only one person mentioned Cassiopeia? She's the most amazing harasser next to Urgot. She's so underrated.

kennen. his kit screams harass...

Q is a long ranged skill shot that deals significant poke early game. it also has a short CD, costs no mana, and chains into your W active AoE.
W passive lets your 5th auto attack deal extra damage and chain into your W active which has a large AoE range and deals good damage. also costs no mana.
E is a ghost-like move that deals damage to everything you run through and can be used for running away and chasing down, as it also speed buffs you. Also costs no mana and can chain into your W active.

Then there's kennen's passive and R which is what hes known for... High damage manaless poke, pretty good chaser/escape, insane CC, and very good sustain once you get spell vamp on him.

By 'bit old' you mean 'over a year and a half old.' Cassiopeia wasn't even out when this thread was started.

Can we please let this thread die? By 'let it die,' I mean stop posting because this thread has no more practical use!

(I wish I could lock threads... )

on the topic of harass, i believe that credit isnt given where credit is due. maokai can not only sustain well with his passive, but his grenades are a wonderful sourc of damage, so if you want harass, just give him a try. its different than a squishy caster, and i for one love the ability to jungle, solo anything, and great teamwork