In his classic Does the center of a golf ball contain a deadly poison?, Cecil mentions the myth that golf balls contain compressed air, and will explode if you cut into them.
When I was a kid, I got one of my dad’s liquid-core golf balls to explode, but not by cutting it. I “accidentally” bounced the ball into a ceiling light fixture, where it nestled up between two then-common 100-watt bulbs. Not wanting to draw attention to my feat, I went away quietly. Some time later the ball exploded, splattering our family room with that white liquid and clumps of tangled rubber band.
I always assumed that heat expanded the liquid core enough to rupture the ball. The rational part of me is glad I wasn’t there when it happened. But only the rational part.
BTW: My older brothers told me the white liquid was lead. I never knew better until just now, when I read Cecil’s column. Ignorance fought!
[In edit: deleted “glass.” I don’t know for a fact that the explosion broke any bulbs. I just always assumed as much because I only got a glimpse of the wreckage before being shooed out of the room.]