I've been looking over all the options in the FW Legion list and I found a hidden gem: Techmarines!

I realised that Techmarines in a Legion list can take Rad Grenades and can be fielded in groups of 1-3 Techmarines as a single unit choice. That's not too shabby when you consider that they're also cheap enough to allow you to take one for every squad in your army without too much of a dent in your points. I decided I had to try it, so converted one up and gave him a go in my assault orientated Reaver squad. This what I came up with just from my bits box:

It's nothing too fancy. The most complicated part of the conversion was making the Graviton Gun (which I gave him to stop him just being a grenade caddy) from a Necron Gauss Flayer and a spare vehicle accessory (I don't even know where it's from tbh), and meshing together Space Marine and Necron legs to make his bionics. After his performance in-game though, I'd say he's earned himself a decent paint job and a general upgrade. Facing a CSM list, the Reaver squad he was attached to managed to kill Typhus and his entire Terminator bodyguard without even breaking a sweat, thanks to the -1 toughness from the Rad Grenades. I can't wait to see how he does against regular marines!