I wanna be the guy is probably the hardest, most frustrating game that has ever been made. The designer actually said to himself when making it "How hard can I make this and will people keep playing it?" IWBTG quickly received a cult following in people that were searching for a game that made them want to smash a lead pipe into their teeth after a few minutes of playing it.
I have been playing IWBTG over the course of a few years, playing for a bit then getting mad and stopping for a month or so. I am finally at the last boss (after 3622 deaths) I tried for a couple of hours to beat him today but gave up when my hand started hurting from pressing fire too much.
IWBTG is free, and is only around 60mb so I would definitely recommend downloading it just to see what all the fuss is about, apart from the mind numbing frustration it is actually quite fun and very funny to play, with references to other games that gives it a sense of nostalgia.
Check out I Wanna Be The Guy here!