I'll start with mine:
My favorite game of all time lasted over an hour and a half. I was Janna, and we played 4v5 for well over an hour and fifteen minutes. Once our 5th teammate's power came back on we tried to get him fed... and screwed up a crucial teamfight as a result. We lost, but I've never had more fun playing this game.
What's your favorite game of LoL that you've played?
One of my favourites was an Ascension game early this year where I was Taric. Ran into a Leona player in solo queue and we stuck together the entire fight perfectly CC-locking people and keeping eachother alive, very satisfying :P
Similar thing happened in a Thresh game back in 2014 where I just clicked with my random Vayne ADC and we both hard carried.
That one time when it ended up being 3 Irelia mains and Riot Baconhawk (who decided to play Jungle karma in ranked).
I remember that just because it was that funny seeing a group of players like that on one team.
the ones where i win
It is two actually, WAY back in the day, back on the old looking Rift, I played AD Sion, shit was fun, got an unofficial pentakill more or less solo, then the other was back with old Mordekaiser, I got a 1 vs 4 Quadra kill, I was REALLY fed.
My favorite game ever was playing as Ashe in season 2.
We had 2 disconnects and the enemy team had 0 gap closers and their ADC was 
who I was already very ahead of, and who was pretty weak back then.
I don't think it takes a genius to know what was possible in that scenario in S2. IE PD LW and fully stacked BT meant I was melting everything.
I'm not even sure winning a 3v5 is possible anymore.
It was a One for All game. My team choose Taric and the other team chose Ezreal. I treasured every second of that game.
the first time i queued into caristinn in ranked and i made his top laner afk
