mobow

Topo maps. Too cool.

Bowfever

Laser Rangefinder. My yardage estimation ability has improved a lot since I've had it. I'm always picking something out, guessing the yardage, and then checking my accuracy with it. I also use it to determine shooting distance to travel lanes and set my stand within my shooting range ability.

NCYankee

Without a doubt, it's my release.

Rob/PA Bowyer

I read this thread several times and I can't think of just one item. Each has a purpose, a need, a use or I wouldn't take it with me. I could continue hunting if I lost any one thing or if one thing wasn't invented. Hell, I did before most of these items and I will if I didn't have them.