I still use Testors, in a tube, when strength of bond is the main thing. They make several different glues but I use only the orange tube plastic glue. Smells the same as when I was a kid, too. As you recall it is a rather runny gel, but it succeeds in really bonding all manner of plastics well - nothing I have found welds as many different types of plastics and plasticy stuff to one another as Testors - but often however leaving visible traces of itself - looking almost like the ripply lines made on metal by a welding torch, because it is a thick, running glue that is often too thick - hard to dab just a tiny tiny bit. On the other hand, liberally applied and left to hard, the two pieces are now one forevermore.
Otherwise, and when I don't want to leave "weld marks" I use Plastruct Plastic Weld general purpose solvent - brush on, in a bottle. They also make several different types and I use only the general purpose (orange label). A note - this stuff is extremely volatile, to the point that it escapes from the sealed (or perhaps not so well sealed ) bottle gradually. If you buy this, check that the bottle you are buying is actually full - I have seen an entire back row of inventory at one local store that had been on the shelf long enough that every bottle was only about 2/3 full. Also if you use some and then screw the top on very well, and put it on your shelf for a year, its carrier fluid will probably have evaporated to the point it is now a thick goo, like in the tube, or thicker.