I personally think you can get meta knight with game and watch. The ability to kill at somewhat low %s, coupled with meta kinght's light weight, makes it a good deal for GW. Also, the bair turtle cancels out the tornado if you aim for the base where his body is. His fair may also do it if sweetspotted.
Against snake....so many chars have a hard time against snake. I dunno. you'd have to think about that one yourself. Even if its a statistically bad matchup, you may do well with a certain character against snake, depending on how the snake plays. For example, I usually try to use lucario against snake, and that usually isnt good news for lucario.
to sum it up, if you wanna beat must meta knight, go game and watch. If you wanna beat just snake, try alot of things but i've heard penguin does well against him. If you want 1 char to beat both...Lucario is probably your best bet, but be warned he has a steep learning curve, so you may not see results immediately