Bridges, teeter totter, flower boxes, side passing or backing thru poles, cones or barrel mazes or weave poles, ground tieing in a hula hoop and walking through a shredded shower curtain. Use your imagination but keep safety in mind. Work slowly with your horse to get him to trust you that the obstacles are not scary. Practice at home with things like ground tieing, spook resistance training and get him to become bomb proof towards seemingly scary things like tarps or plastic bags or shiny things. You never know what challenges you might face at a horse show and the goal of halter obstacle is to make it a challenge. There are some good books out there with ideas for obstacles and with photos from actual shows that can get you started. Have fun.