The primary reason for LoL's popularity is its accessibility. League of Legends is one of the first video games to introduce a free-to-play model to success. They released the game without any price tag. Instead, the company monetized through cosmetics that provided no in-game benefits aside from aesthetics.
The best item that League has had this year is a matter of opinion, but the old Statikk Shiv is definitely a contender. It was a powerful offensive item that gave champions a lot of burst damage and waveclear. It was especially popular on AD Carries and AD Assassins, who could use it to quickly take down enemies and push towers.
Here are some of the pros and cons of the old Statikk Shiv: