ok, heres a gimmick of a charizard set:
charizard @ leftovers (M/F) blaze
calm: 252 sp.def/ 130 hp/ 55 spe/ 65 sp.atk
gives: 295 sp.def/ 329 hp/ 249 spe/ 270 sp.atk
role: special support
will-o-wisp
toxic
substtitute
flamethrower
HP Ground is an option over anything but will-o-wisp, which is useful for physical sweepers who can't OHKO you, but maybe 2-3HKO you. toxic is good for breaking walls like blissey and suicune, who aren't bothered by burn, infact, possibly benefit, with burn, they can't be paralyzed/ frozen/ poisioned. substitute allows you to survive a hit from someone who will OHKO you, you must be faster of course. flamethrower is needed for skarmory and levitate bronzong, who can't be hit by toxic, don't mine burn and can't be hit by hp ground.
counter list, and how to deal with them:
Tentacruel:
without hp ground, i suggest running, now seriously, sub on most switches to keep a good defense, so to defeat this, make sure you have a sub, or atleat max hp.
on max hp, you may survive a surf, not likely, but you can gabmble, you will strike first usually, standard tenta runs 36 speed evs, with the same base speed, and your both using calm, you will outspeed them.
hp ground will probably 2HKO, so surving the first hit is vital, but remember after ko'ing tenta, your weak and open.
unless you sub the turn before it attacks, then it will kill your sub while you 2HKO it, so... have fun sucking earth tenta
Thick fat pokemon/ water types:
RUN!!!! you have no way to defeat them, hp grass is not an option, so just run.
for thick fatters, they eat flamethrower well, i suppose burn will scare snorlax, but hairyama can take status, with guts, so its not itelligent to keep him in.
heatran, nintales, arcanine and houndoom
the first two can eat hp ground, heatran, without hp electric really can't marjonly damage you without exploding, and a charizard is not a worthy explosion target, i imagine heatran will expect a switch, possibly even launch a earth power, when you stay in and hp ground his ass, you will looked upon with much shock.
Nintales stands less of a chance, when they switch him in they'll expect you to run, and probably np up, hp ground for the K.O. and smile smuggly.
now arcanine is the tricky one, you need to have alot of prediction, predict whether its physical or special, if its special, take the hit, that probably won't OHKO you, and k.o. back with hp ground. if its physical and you stay in, your dead, you will fall to the likes of thunder fang or extreme speed, so yeah, beware the large dog.
houndoom is the same as nintales, but with less chance of surviving / doing damage with dark pulse. lol.
tyranitar and hippodown:
run, hp ground does shit all to tyranitar because of the sandstorm boost, so no hope there, hippo just hurts because of the likeliness that he will set up sr, and possibly start phazing you, while your best come back is w-o-w or toxic, toxic may ward him off, but you will have an ever going sandstorm to deal with.
stealth rock makes you cry, taking 50% of your hp, so don't go switching with SR around.
anyway, the idea is to switch into a grass attack, sub, then status/ hp ground/ flamethrower the switch.
btw, if someone could get exact caculations, that would be great.