It's far from cutting edge these days, but back in the 80s, something like the Korg Monotron synthesiser could well have got you on Top of The Pops.
Using the same analogue filter found in the legendary Korg MS-10 synth (an instrument of choice for synth bands 30+ years back), this battery-powered keyboard packs an easy-to-use keyboard, an internal speaker and headphone jack plus voltage and low frequency-controlled oscillators for creating those crazy vintage-style synth grooves. You can also filter and modulate sounds from other external sources via the audio input jack.
It could be too much fun. Available online, it sells for £59.99.