When you decide to experiment with a build that seems kinda stupid

built runic echo's sion. Game was hilarious.

AD Bard.

I like the builds that you're so ungodly lucky that you got enough gold early to pull off, and then make you unstoppable.

Full armor pen crit Garen. Q can instant kill a squishy. Early game is 100% ass.

AP attack speed tank Xin. Good luck killing me.

Or back in the day, 5 Sunfire Eve/Twitch. 60 second stealth and you just walk next to someone until they burn to death.

My all time favorite was tank Teemo, with his only offensive item being Frozen Mallet. Brings a whole new meaning to unkillable Satan.

Edit - Forgot about back in the day when PD gave dodge, and my team was Nasus, Ashe, Xin, Shen and Taric, vs a Jax who got fed enough to get enough PDs to give him 100% dodge. Literally unkillable lol.