WARNING: If you are a little squeemish of needles you might not want to click play.
Pulp Fiction is a massive, epic story of the LA underworld. It involves, gangsters, rapists, thieves, and every other kind of low life you could think of. All the stories intertwine. You could name about a thousand movies that copied this formula after 1994.
Prior to this scene, Mia Wallace (Uma Thurman) has accidently mistaken Vincent Vega's heroin for cocaine and snorts the heroin, which causes her to have an overdose.
The next scene (the one above) Vincent hurries to his local drug dealer, Lance (Eric Stoltz) to get an adrenaline shot so they could sace Mia's life.
The scene handles realy dark tones with this very uncomfortable It's kind of saying to us "should we really be laughing at this?" Check out some Quentin Tarrantino (director) does with some of these. Just look at how uncomfortably close he gets to the faces of Travolta, Stolts, the needle. It adds to the heightened sense suspense. You have a hard time watching it, but you're absolutely fixated on what's going to happen.
PS I just love the body language of Lance as he watches Vincent drive his car right through his lawn. It's just so "Look at what this asshole is doing".