The year Scooter was a yearling he climbed the tree, and pulled off the glass balls to play soccer with down the hallway. As each one would shatter he'd push the buts for a minute and then go get a new ball. That year I lived in a house with a sliding glass door to the back deck. The tree was moved outside, onto the deck. I could watch the lights twinkle but it was safe from Scooter. It snowed around Christmas that year, and boy was that tree pretty! Covered with snow the lights glowed through and it was just lovely.
Current yearling cat doesn't try to climb our tree, but we have the fragile ornaments on the top of the tree and the cat-safe ones at the bottom of the tree.
Haven't used tinsel since my first cat, Puff-n-Stuff, left me tinsel wrapped 'gifts' in the litter box....