The movie was about one parasite creature invading into other people's body taking full control of them and making them very tenacious and moving from one person to another. When person that it lived inside died, it had to move to other person's body.

I can think of 2 like that - Brain Damage and The Hidden. There's probably more... can you remember any more details?

I remember there was sexy woman and that parasite snake alike with about 5 legs on both sides invaded her. She was invincible and got a lot of bullets but she was still standing with a lot of holes in her body until creature left her body. And every time that creature wanted to move from person to person, their mouths were opening wide so creature can move from one mouth to another.

Sounds like

The Hidden

Even though the alien switched from
Body to body, it showed the same
Love of fast cars, loud music,
Mayhem and senseless murder.

view trailer (http://www.youtube.com/watch?v=UHIwsaFhra0)

Could possibly be The Tingler. This is an old movie though.. black and white.