Not the most exciting place inside, but a lovely rooftop area which not all that many people seem to know about, 2 mins walk from Old St station. If it’s packed then The Red Lion is just up the road.
Slightly biased as this is where I live, but Stoke Newington is great place to spend lazy saturday / sunday afternoons getting sloshed with friends. There are 10 + pubs within walking distance who all are great places for one reason or another. I'll pick out the White Hart for its huge beer garden...
It doesn’t happen very often but its one of those things that brings people together. Running to the park or hill with anything you can find that might work as a sledge with a big grin or your face.
This may not be much of a secret but deserves a mention. I find it hard to go anywhere near this place without having to go there. Freshly baked Beigels hot salt beef and it never closes, 24 hours a day 7 days a week.
Lots of traditional charming country pubs around the area, but it can a bit hit and miss. A really friendly one with amazing food (and a unusually large veggie selection…) is the Beehive in Epping Green; close to the Great Wood. It's friendly enough you dare going there by yourself with the paper and are not at the mercy of local rubbernecks ("the rubberneck" = person who stares at strangers without any sign of guilt)
One of London's best kept secrets, Spiritual Bar is a small and super welcoming live music bar on a side road near Chalk Farm station. Always somehow busy but not too packed, they play host to most of London's best emerging blues, rock and folk musicians, and owner Raf is the nicest dude you could meet. And makes a serious mojito