Picked up a little Yamaha SHS-10 keytar for 20$ from a thrift shop one time, thinking it was only a toy, but a cool novelty item. After a year or so I saw an ad here on TB with a picture of it, so I decided to further investigate my little keytar that had been sitting in the closet for the past year, and found that they are actually fairly sought after little instruments and go for upwards to 150-300$ due to the high quality midi-out capabilities and other cool features. The only thing is that, while its a decent little keytar, its hard to sell to someone unless they know what it is, since it does look like a toy.
But there is alot of fun to be had with it when hooked up to a midi synth program (or whatever you call it) on my computer, and in true 80's epicness, the built in demo tune is Whams "Last Christmas," lol.