Poll Results

Total votes: 2128

Sexual intercourse: 476 (22.4%)
The invention of writing: 475 (22.3%)
Clean running water: 316 (14.8%)
The Allosaurus: 282 (13.3%)
The Lord of the Rings: 146 (6.9%)
Chocolate ice cream: 128 (6.0%)
Winning the lottery: 117 (5.5%)
Anaesthesia: 70 (3.3%)
Summer vacation: 61 (2.9%)
A perfectly ripe, sweet peach: 57 (2.7%)

Oh my. The Allosaurus didn't win!

Although someone did hack in "The Allosaurus" as the answer, even though it was already there in the list of options...