triping

We have wooden floor downstairs and carpet upstairs.

LEGO. Have you ever trodden on a lego brick, nuff said!
Little plastic soldiers. As painful as LEGO, but not as durable, so not only do you end up with a sore foot, but an unhappy child too
Paper. The last time I slipped on a piece of paper I broke my big toe. On wooden floors, paper or magizines means a slip hazzard and you will often find me legs akimbo on the floor
Wet patches. Thankfully now my boys are five and six these patches tend to be drink, but in the olden days you never knew what you might be stood in (I will leave that to your imagination)
Cars. Oh yes cars can soon have you propelled across a room at breakneck speed too