Well, The Tick Key has a thing which would be very hard to duplicate.
First, it's so cheap why would you want to try and make your own; but second, the area where the tick's head is is tapered downwards so it isn't just flat. Then it tapers into a little specially-shaped area and is just the right amount of sharpness so it funnels on either side of the tick's head without shearing it off. The slight bend downwards cradles the head as you pull and the not-quite-perfectly sharp edge pulls the mouth parts out instead of just slicing off the head.
That's pretty particular and I'd say I, who is very good at the use of a Dremel tool, would have a hard time replicating those angles.
I generally buy what I couldn't possibly make. They did a wonderful job designing this tick tool; and it's amazingly cheap.

