If I got it right, Pascal's Wager states that even if there is no proof for the existence of God, one should act as if they do believe in God because if they're wrong, they lose nothing and have the same result as a person who didn't believe in God and was right, but if they're right, then they get to go to Heaven and party with the angels. On the flip side, if you don't believe in God, you run the risk of being wrong and going to Hell to party with the devil.
In other words:
Believe in God, just in case, even if you don't really believe in God, act like you do.
There are two things wrong with this, the first being that people who follow this advice believe they're able to trick God. If God really is as omniscient as his followers claim him to be, wouldn't he know that you're just lying? And wouldn't that make it worse? I'm pretty sure that lying itself is a sin, you'd have to think that lying to GOD HIMSELF is a big no-no. Unless God's just a narcissist (with a violent need for attention and he doesn't care whether you truly believe in him as long as you say nice things about him), he'll just send you to hell along with the other dirty non-believers.
Then there's also the problem of the fact that, if this is true and that all it takes to go into Heaven is pretending to believe it exists without any actual proof, then God is no better than (what
G0dItself likes to call) an abusive husband/wife. They don't really care if you love them or not, as long as you act like you do. With a being so, supposedly, omniscient and caring as God, you'd think he'd give you a little bit of a leeway when it comes to believing in him before you die and go to Heaven (or Hell).
By far Pascal's Wager has to be one of the most immature arguments for a belief in God, requiring nothing more than a fear of Hell.