I made the "orbital laser drone" that I'm sure is nothing new for folks. For those who have not seen it, it works as follows:

Base: 1 Hover Stone with something else on it to add a bit of weight. I just use a second hover stone.

Weapons: 2 Construct Heads attached to the left and right sides of the Hover Stone. To each of these Construct Heads, attach as many Beam Emitters as you can get away with. I put 7 on each side for a total of 14.

Lift: Attach 1 rocket to the rear of the base at a 45° angle, to shoot the satellite up and forwards at whatever it is you want to kill.

It's very effective at killing big enemies like Gleeoks, provided you can evade their attacks for a minute or so. If the drone dies before the enemy does, just time reverse it back in place and let it get back to work.

Problems I have encountered: As enemies like Gleeoks may occasionally take to the air, they can bump the satellite and send it drifting out of range, despawning it. Can be mitigated by attaching a dragon scale, but that adds extra work. The drone is also very expensive to entirely autobuild, using up over 100 Zonaite. I haven't found a more effective means of obtaining large quantities of Zonaite other than by slowly collecting it manually in the depths, so the drone is currently used sparingly.

Other than that, the 9 Zonaite budget hoverbike is my only other saved favorite schematic. It took a bit of tweaking the fan/steering stick placement just so, but I managed to get one that flies perfectly straight and handles really well. I just lament the fact that I fully explored the depths before learning about that invention, which would have made navigation so much easier. But it really sped up a lot of the later overworld/sky island exploration I did, though, and makes delivering objects/crystals/Koroks over long distances a breeze.