Great ideas and I just so happen to have all 3 of those improvised gardening tools at my disposal!
Just never considered their use in the garden tool kit. I do keep pliers in the arsenal, from bending/snipping wire to tightening shears and loppers. Gardening for a living I like to keep as much as possible in "the bucket" to avoid trips to the truck.
Another "must have" for working with plastic tarps (especially on windy days or working alone) are the plastic and steel Coleman tent stakes. No more fly-away tarps! One recommended improvement is to hit them with some hi-vis paint. These would also likely serve as the spike bayonet does giving them a bonus feature. Sturdy and reasonably priced too.
