Quizzing
I quizzed pretty actively throughout my school and college life. Although the frequency of taking part has declined, I still love setting questions for quizzes.
Quora
I write here (more like used to write) on Quora and try to actively contribute to what I feel is a wonderful community. I write mainly on mathematics, music, soccer, and languages, linguistics and etymologies.
Music
I've been playing the electronic keyboard (synthesizer, if you please) for 8 years now. I try to express myself through the instrument. Since February 2017, I've been playing the ukulele, and am falling in love with it a bit more, every single day. I have 3 ukuleles in my collection, a Diamond Head DU-150 Soprano, a Luna Tenor, and a Mitchell MUB70S Baritone. Among other musical instruments, I can also figure my way out around a guitar, Seagull Merlin, mandolin, Appalachian dulcimer, and a harmonica. I love Bangla Rock (see this and this to get an overview), hard rock, heavy metal, and progressive rock and metal. See my SoundCloud profile for some of my covers.
Table Tennis
I formally learnt the game for 5 years when I was in middle school. Since then, I've been playing it at an amateur level.