I've got sooo many handy things! Most of my handiest things are pretty, shall we say, low-tech:
I have many uses for a piece of bamboo
I have bubblewrap plugging up a badly-placed outlet in a rainbarrel, as well as insulating 'uncurtainable' windows
Old cotton sheets torn into strips are really handy for tying up tomatoes and raspberries, coralling fava beans...
at the end of the season the whole lot can go on the
compost, or break down in place.
Hmm, this list looks more 'frugal', than 'handy'
Ok, officially handy: my multi-screwdriver: never again will I stomp back to the shed muttering #@#$%^^&Phillips, squaredrive etc