I would like to know why he is able to do pretty much anything. He seems to be almost unkillable, except when Gon surprises him. I am only on episode 4, so try not to spoil anything please :)
You're right to think he is NOT just another participant. He is already at hunter level which co-incidently includes several other participants in this exam as well (Good luck figuring them out!). As Happy Face said, you'd need to see more to understand the actual mechanics between the "magic" Hisoka(the Participant 44) uses.
To give you a bit more info without spoiling anything. I'll block quote the wiki intro about Hisoka on HxH wiki.
Hisoka is portrayed as entirely self-serving, self-absorbed, and selfish; he does whatever he likes as long as it pleases him in some way. His insatiable love for spilling the blood of powerful fighters in combat and his enjoyment of extreme pain while doing so fuels his seemingly sadomasochistic desires. In order for them to grow to their full potential (so as to improve the pleasure of killing them later), Hisoka allows the main protagonists to live in situations wherein he is easily able to kill them. Likewise, he grows excited to meet any new people he deems worthy of fighting or anyone with potential to be a good fighter and entertain him in the future.
Long story short he is an anti-hero, who is completely self-centered and a Sociopath. He is one of the best characters in HxH viz. saying something as HxH has great character development!
Edit: Just saw your username "DeadPool" and Hisoka fits the role of Deadpool in HxH universe.