A construction toy chain thing. It makes a good desk ornament, fidget toy, cat amuser, whatever.
It's not exactly a "construction toy" because once it's constructed it can't be changed, but that's the category that matches the best.
Print a bunch of links, preferably in several colors. Fit them together, melting the tips of the pegs to keep them together.
How I melted the pegs: I have a scraper thing I use to peel prints off the bed. I melted the tips of the pegs with a soldering iron, and then mashed them flat with the scraper to give them a nice flat top.