I would not counterpick GP with Irelia. Any champion that is very weak before 6 is at best a dice roll versus GP. If he takes ignite and he plays properly, he may either zone you or first blood you and you will be behind all game. Irelia cannot confront GP's parrley spam before she gets her ult; he simply hits harder than she does early on (and he has more hp, since he's GP). So Irelia, Nasus, passive farmers like those should lose lane to a GP who is aggressive enough early on.

I think the best counterpicks are champions who can outplay him early. Yorick can outsustain from level 1. Garen hits hard enough to zone him even early on, and sustains well enough to eat the parrley spam. Etc.

Thanks for the help so far, guys.

Yes, my assumption is no help from the jungler. Not because of normal queue, but because even in a 5 man premade, sometimes the better ganks are elsewhere. I want to know who I can best use to dominate 1 on 1 against the good top laners.

Since you're disagreeing on how hard a lane GP is versus Riven, who would you say her hardest lane is against... and who would you use to counter THAT champ?

A lot of Yordles are strangely made to be anti-top lane. Teemo and Kennen are counter picks for most top lane champs. Teemo is actually one of the most effective counters to top lane Tryn and Riven, due to his range, blind and passive. Kennen is just OP top lane as seen in the last few tournaments. Rumble is good in the way that he ALWAYS push the lane.

Huh. I've never had a whole lot of problem with Teemo as Riven, though I've not had to lane vs one yet. So much of my damage comes from my abilities, the blind isn't as big of a deal, at least for its duration. I just save my passive stacks until it's done.

Probably more of a pain to lane against, though.

Riven is a very strong, if not the strongest, solo top in the game. AD scalings galore. Lee sin counters akali nicely though, just so stand in her shroud and cast tempest, free vision.

Renekton craps all over gp

Renekton beats GP
GP Beats Irelia, Riven, Panth, ALL AP
Nasus beats anyone with a bad early game
Ryze beats anyone who needs to farm up (provided you have the right runes)
Riven counters most, but gets destroyed by GP and Garen
Wu Kong is very sensational top, and takes a ton of skill, but can do well vs most
A Strong rumble can lane against pretty much anyone
Lee counters anyone with lack of sustain
Udyr counters bursters
Teemo counters most tops but takes enormous skill to be good at him with top
Kennen lanes well withanyone, specifically counters AP sion

Play around, watch ranked matches, and see what wins constantly vs certain things

Pantheon counters GP. Passive opz

edit: Just gotta play aggressive and hide in the bush. And cs whenever you can to build up your passive.

Beats GP:
Pantheon. Aegis blocks Parrrley.
Nidalee
Urgot
Cho'gath
Galio _can_, but you won't want to use the usual MR-heavy runepage.

Notably, Ryze beats Kennen or Singed, and Vayne beats Singed and the very occasional solo-top Karthus.

Cho'gath, Nidalee, and Urgot are virtually uncounterable.

Galio doesn't win every lane, but he very very rarely _loses_ one. A fair number of champions can force Galio under his turret. Hardly any can keep him from farming happily there.