Greece: Easter. The tradition involves celebratory gunfire in the churchyard at Easter Midnight Mass. The modern manifestation of that is fireworks being let off in the packed churchyard at Easter Midnight Mass. Both in Greece/Cyprus, and in the diaspora. The news each year reports people being injured (or killed) as a result; my sister has had her hair set alight at least once.
Australia: New Year’s Eve. There’s an attempt to do so on Australia Day as well, but New Year’s is the one that has captured popular imagination. The ABC makes a point of broadcasting shots from each capital city (and some random small country town), and it used to be a station promo.
Sydney’s are the most spectacular. Fond memories of being in a train in Sydney, and overhearing a family saying “we’re gonna go down to watch the crackers!”