The authenticity of the latter portion of Mark 16 is disputed. If you believe that it's inauthentic, ignore that for now, and for the sake of discussion, assume it is authentic.
In Mark 16.17-18, Jesus says that his followers will cast out demons, they will speak in various languages, they will "take up" serpents, they will survive any "deadly thing" they drink, and they will heal the sick.
There are a few churches on the "edges" of mainstream Christianity, who take two of these totally literally. Specifically, there are churches that teach that Jesus was telling his disciples that they could handle snakes and drink poison and not die from either. Some of these churches, for whatever stupid reasons, go out of their way to do these two things, turning Jesus' commands into nothing more than an entertainment venue for the congregation.
What I'm trying to say is... what purpose to the Kingdom of God does picking up snakes have? How does going out of your way to show off that you can handle snakes edify the Church? What sense does it make for a follower of Christ to get on the stage in front of the congregation and prove that they have real faith in Jesus by intentionally drinking a toxic liquid?
So my point is this: when Jesus told his disciples that they would handle serpents and survive drinking poison... did he mean that as literally as people nowadays interpret it to mean?
In Matthew 17.20, Jesus told his apostles that if they "have faith like a grain of mustard seed", they could command mountains to move out of their way. But in all honesty, what purpose would moving a mountain have for the Kingdom of God? In what way could such an act edify the Church? I think it's plainly obvious that Jesus was using the "mountain" as a metaphor for obstacles in general. That he didn't expect the apostles to literally tell mountains to jump from one valley into another, but that if they truly had faith in God, that God would help them overcome any obstacles.
So, back to snake handling and drinking poison. Did Jesus honestly expect his followers to go out of their way to find snakes to pick up and show off with? To go out of their way to prove their faith by drinking poison? To be honest, I believe that no, he did not expect his followers to literally do these things. And I think the Christian who does is seriously misguided in reading what he was commanding.
So what would Jesus be meaning, then? We know that Jesus called the Pharisees "vipers" on occasion, and that "snakes" have been a timeless symbol of deceit. Maybe Jesus was using "snake handling" as a metaphor for his apostles to "handle" the Pharisaic vipers? And what about the "deadly drinks"? Does anyone else have thoughts on the subject?