Warpsmith

They're basically a cross between Professor Oak and Doctor Octopus.

No, sir, totally not a Warsmith.

The new plastic one.

Warpsmiths (not to be confused with Warsmiths) are basically Chaos Techmarines, introduced in 6th edition. Many of them are loosely allied with the Dark Mechanicus. Unlike Techmarines (who revere technology), Warpsmiths attempt to subjugate it. They are also masters of fusing the daemonic and the physical, which, in layman's terms, means they inject Chaos into all their warmachines.

Overview

Warpsmiths tend to be obsessive and believe that mankind's destiny is limited by his mortal nature, and thus they see combining the power of Daemons with the mechanical and organic as the answer to circumvent this problem.

Because of this, all Warpsmiths are engaged in an eternal quest to combine the strengths of all three of these elements -- mortal, daemon and machine -- whilst eradicating their weaknesses. They would conquer the galaxy and remould it into one giant, tainted flesh-engine if they could. The Warpsmiths themselves seek to embody this unholy fusion of man, machine and daemon; in their search for perfection, they often become more metal than flesh. Some Warpsmiths are little more than a brain and a spinal cord wired into a metallic approximation of a Chaos Space Marine; pincer limbs, Mechadendrites and fusion claws sprout from the Warpsmith's altered form next to Melta crucibles and searing welder blades. Sometimes, some Warpsmith can go one step further and equip himself with a Servo-Harness for the more heavy-duty shit.

Unlike Warsmiths (who, per Iron Warriors tradition, replace mutations with bionics), Warpsmiths have bionics from being actual Techmarines.

They are also to thank/blame for the various types of Daemon Engines that blight the Imperium of Man, Cybertron, and the land of Kanto.

Now comes with cavalries.

Crunch

On 9th Edition, they are your Swiss army knife man with a pimping new model! For 10pts less than a Techmarine with similar loadout you get +1W, +2A, +1Ld. That includes a Hand flamer, an Inferno pistol, a Plasma pistol (any of which you're unlikely to ever fire), 2+ Save for his Artificer Power armour, a Fancy Power axe, and Naughty tentacles for some extra melee pokes. All this kit lets him hold his own against small squads of MEQs bully in CC things that don't know how to fight, in the unlikely scenario you ever get into said CC.

Read, he can maybe shoo away cheap Deepstrikers from the tank he's been assigned to support. He has (sigh, say it with me) no mobility options, so he's usually stuck wherever you deployed him. With so much kit for what you pay, he can slot in pretty much anywhere and contribute, though it can often be hard to determine where he'll add the most. Or you could just let him do his damn job and have him repair your vehicles for d3 lost wounds each turn and give them +1 to hit with ranged attacks only (If you're looking to buff melee attacks, take a look at Lord Discordant instead), in an edition that's largely stripped that sort of bonus away from them.

Alternatively, he can ride shotgun in a Land Raider that, once it deposits whatever it was carrying, he can then repair and ride off in to go sit on objectives. Don't overlook this guy. The only wargear option Warpsmith has is switching Exalted Power Axe to Thunder Hammer if you're feeling saucy. Combi-weapons have been thrown into Legends however...