Icons for content that is currently in
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Diamond Pickaxe Upgrade (for tool)
Aqua Affinity Upgrade (underwater mining speed)
Water Electrolyzer (rebreather)
Step Assist

Icons for stuff which will likely be added soon
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Laser/hologram projector (to be used as a component in the cosmetic as well as HUD upgrades)
Force Field Emitter (component in shields and possibly some other things)
Control Circuits (but can use the tier 1 special battery thingy ... although a variety would be ideal)
Carbon Myofibers (artificial muscles)
Heat-resistant plating (maybe made of tungsten or similar)
Cooling systems

Icons for stuff that will be added eventually
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Generators of various types (kinetic, coal, uranium, fusion...)
Fire-based weapon (flamethrower?)
Lightning-based weapon (lightning arc thingy?)
Sound-based weapon
Energy beam type weapon