Well... there's hydrazine (N2H4) which is the stuff they use as monopropellant rocket fuel. It burns even without the presence of oxygen and it's even more toxic and explosive than ammonia. It's the reason the capture crews for returning spacecrafts wear hazmat suits.

However hydrazine is liquid at room temperature and it can be converted to hydrazone (also being considered for fuel cells) which is solid at room temperature and non-reactive... until it comes into contact with water at which point it all turns back into hydrazine.

But yeah no there's really not a "nicer" fuel. Generally, if it has nitrogen in it and it isn't literally just nitrogen with itself, it's dangerous. And the more nitrogens it has the more dangerous it is.