I broke a glass at someone's house on Saturday. It was a shit glass anyway.
When I was 12/13 I broke a pretty expensive lamp round some girl's I was trying it on with (probably hoping for an outside chance of fingers in knick knacks).
About ten years ago I broke a large umbrella stand in a Cypriot restaurant (in England). The owner said that it was the last thing his wife gave him before she left. I do not know if this is true.
What property not belonging to you have you broken?