Picard hit by a snowball
A snowball was a spheroid projectile made of compacted snow.
Upon discovering "Archer's Comet" in 2151, Trip Tucker called it "one big snowball". Later, when Malcolm Reed and Travis Mayweather discussed what to do on the surface of the comet, Mayweather suggested a snowball fight. (ENT: "Breaking the Ice")
In 2364, Jean-Luc Picard was surprised by a snowball to the cheek as he encountered Wesley Crusher and his friends exiting the holodeck at the end of their ski lesson. Their apparent snowball fight had gotten out of hand. (TNG: "Angel One")