Depends on the deer. Mule Deer here that you can find the front yard of your house can be 200-300lbs. And depends on what you mean by, "deer". Are you think about reindeer? Elk? MOOSE? Hitting a moose is gunna be a bad day.
Also, in various parts of the world, the names are commonly used for different specific animals, which can be confusing. What's called a Moose in say, Sweden is called an Elk in Britain. But what we call elk in the US are a different species entirely. Elk in the US are another name for the red deer species, which was once considered merely a subspecies.