Casio Casiotone MT-65 by lu77
This is THE casiotone to get, it has the most knobs sliders etc to exploit the chipset which has a warm sound and fair breadth to it for a "toy". This keyboard has two types of envelope shapes which can be used in combination, 12 fixed drum patterns, 20 voices, sustain, vibrato, and 1 finger chords. As well as the bass and arpeggio accompaniment in all Casiotones, particularly good for their convincing Polka.
This is a very musical lightweight and portable instrument with headphone jack and line out, battery operation or 7.5v dc. The key is the portable speaker which gives easy access when you just want to try something out. The line output (mono RCA) is noisy as hell. you can experiment with battery operation or dc to see which is best or use the headphone out.
There aren't many useful chip mods on this one because the keyboard uses all the features already.
The organs and horns are particularly good at holding a melody over a noisy band (if amped up) sounds great with guitar pedal experimentation too. It's lo-fi its not everyone's taste, yet you'll spot these guys in so many famous DJs studios, near-at-hand to work out a simple idea.
The minute mine dies I will be on the hunt for a replacement.