Tommy, it's actually "poison ivy" but my mom always called it "poison ivory" also.

If you're allergic to it...as most people are, you will likely get the dreaded rash if you try to dig it up and move it. It does have to have a root system.

Many people don't recognize poison ivy so it wouldn't necessarily deter someone, just make em itch like h*ll for awhile...which would surely serve them right.

There are plants that have thorns and barbs that would indeed put a hurting on a person. Rose bushes come to mind. Others such as barberry and some hollies can be very painful as well. Please take a look at the link below and maybe you'll find something that will appeal to you.

Here is a link that might be useful: Keeping your home safe

Or try black raspberry, grows well in shade, nasty thorns to deter thieves and very tasty berries for you!