Unlike the other two Cool Youtube Users I've mentioned, I have only just become aware of PewDiePie's existance... And that was due to my fascination with Happy Wheels. In any case, I found PewDiePie and have become a "Bro" due to the clicking of the "subscribe" button and with that comes great responsibility to sit through about 30 minutes of videos from the youtuber... And I love it!
A bit of background info would not go amiss, perhaps; PewDiePie is a Swedish guy living in Italy and he releases gaming videos of him playing (mainly) horror games with other video games coming in to lighten the mood. Despite the use of horror video games, PewDiePie always makes me laugh in his videos with his amazing reactions to anything scary (escpecially Slender XD) and his constant stream of obsenities in his wacky accent that just makes the whole experience very enjoyable. It's not just that though; his gf plays in some videos with the comments full of "THEY MAKES SUCH A GREAT COUPLE <3" etc. and they do seem to feed off each other (in the comedy sense)
As mentioned before, he has played a horror game called Slender about 10 times over all in 5/6 videos... The link below is for his first Slender video and it's the one that got me hooked on the Swedish youtuber... Tread carefully :P