Anything - I have several guitars including 2x Ovation electro acoustics which came in trades, an Aria semi acoustic, a very nice HB Tele with Bigsby, a X-men Peavey (I'm a comic collector) and a half size guitar bought to convert to a bass before realising it would cost more than it's final value.
I've had numerous saxophones - but you need to play regularly to get the most from them - I don't. I have a Yamaha Venova Soprano which occasionally comes out, only to be put away before I annoy the neighbours.
I bought a tongue drum a while back - it sat on the living room table unplayed for a while before I put it away. Love the tone but the time spent learning to play it is better spent playing a bass.
TBH I'm not good with money and find any excuse to impulse buy.