Krookodile
Skeletron Prime
I am not a very good mechanic in Terraria but a cool trap you could add a boulder that attaches to wire and moved with the wire, although you could just make a boulder that attaches to chains or ropes. Boulders are unfortunately ineffective in the moons because you can only use them once, so maybe a way to use them in a different way? And finally a bouncing boulder! once it starts rolling it keeps on bouncing back and forth so that you could make it hit buttons and other things like that (including enemies!),