I’ve still been thinking about this off and one, and I think I’ve decided that the best yoyo to give away is the whip, or the butterfly XT, and also give them some fat string with it to aid in staying responsive the longest. In my classroom box, the ones that get played with the most are the butterfly XTs. (edit* not anymore. Kids love MYY.)
I got to play with @Slestak75’s kit of modded responsives, and I think the whip is the closest stock to his setup with a THICK string. Really impressed that his entire setup has been unmaintained for the entire time it’s been out. If I come up with something that is under $10 total that is modded and just a workhorse that needs no/little maintenance, I’ll post it.
My current go to give aways are YYF whips, and butterfly XTs.