ok this is my best matchup in the game, because everyone in new england plays snake, including the best snakes around (cort and pc).
first of all, if you try to be near snake, you'll die, simple as that. I've seen pc and cort deal like 60 damage in one close combat combo, which is devastating. Basically if the snake player is any good they will do combinations of the first to jabs, the ftilt knee, and grab to dthrows to deal insane amounts of damage. Also as you know, uptilt will kill you at like 80 dmg... for your own sake, stay the f away from snake.
use your spacing extremely well. if your range your turtle against their sheild you can land and sheild before they can get an ftilt or a mortar slide out. If they ftilt your shield you can sh a bair fast enough to hit them thus punishing them for an ftilt (finally someone can do it!). dtilt works sometimes to cancel out the ftilt, but i think the ftilt might be 1 frame faster or some miniscule amount.
set your spacing up at distances, a lot of snake players love to mortar slide when at a medium distance, have a fsmash waiting for them, trust me that works.
grenades are too easy to avoid to worry about. people think snakes away game is amazing, but its really only mediocre at best. you know when the grenades will explode, so just airdodge, etc. Just watch for mortar slides really.
**** his recovery with nine hammers or fairs (i do this more cuz its more consistent, although hammers 4 through 9 i think will knock him out of his up b). If they go mid height recovery-wise, then fair or hammer, if they go low near the stage then grab him or spike if he's just far enough away to be grabbed. If he goes too high, then use your up air as he's coming down to throw him off, or if you think you can land it, get an up b in there, its tough to dodge.
snake can't really edge guard you at all. The only thing i've seen that might work is a run off bair (you have to be recovering away from the stage for it to maybe work, so just learn to hug the stage when up-b'ing) or a ledgehog and then a dj aerial when you land, but those both only work sometimes at best.
get your kills with smashes obviously, but im pretty sure that the fsmash seems to work the best against snake... move's just too quick.
learn your freakin nair/upair/uptilt combos, those help to rack up damage, which you need badly.
avoid the uptilt... for your sake. they will kill you with this 80% of the time, other 20 is random moves like ftilt, bair, nair etc.
from what i can see, good snake players don't dsmash or mine on the stage unless they are stickying. if they have c4 on the stage and get knocked off its gunna be bad news for them. dmash is just too slow imo, so i would just grab them just as they are done putting it down, they get hit by the explosion (depending on controller port?) and i combo with nairs after for lots of damage.
i recently beat cort (one of the best snakes in the nation, it was really friggin close, but reguardless) at the last tournament, so i have a great deal of experience in this matchup. I personally feel that its neutral, actually more neutral that mk now, i think snake does better, but this one is like dead on 50/50, whereas i think mk is like 53/47 or something like that in gw's favor : ) hit me up for questions