Irrational Number Line Games, LLC
We start with a Space Marine holding a bazooka. (Missile Launcher? Well, some type of heavt, OTS weapon). And I glued a spear into it. That's going to become a harpoon.
To really be a harpoon, we need to conntected to a line or cable. So I am making some spools. I have leftover cross-stitch floss from SWMBO. I tied an overhand knot, wrapped it around the stick a few times, and added another overhand knot at the end.
Now I add a coat of PVA (cow glue), one of sliver paint (because they are going to be wire cables), and another coat of pva. This will help the spools keep their shape when they come off the stick.
I cut the short end off the spool and glued them on to harpooner bases.The thread is too long and not painted all the way. I will wait until the spool dries on the base before I trim it. I will take two or three tries of snipping a bit of the end, then test fitting. Otherwise, I would likely cut it too short. So just progressively moving it back until I get the right look. BTW, I was a naval officer, and no way in Hell would I let someone straddle a line like that. Apparently Space Marines have never heard of OSHA.
I had four dudes, so here is back side, front, and other side. I like how much line I got in it. Enough to make the point, but not line going everywhere.
So, what do you do with SM Harpooners? Well, the obvious first idea is the harpoons dig into a vehicle or mech and either (1) reel it in or (2) hold it fast. I like the second idea. Three or four SM trying to hold down a big unit. Beyond that you could send something down the line like a shock or a plasma blast. Bigger bang, but it takes two turns and gives the opportunity for the target to break away. It could also be connected to a device that hacks the target. Again, a couple of turns and successful attacks required to take control of an opponent tank or mech. It could also be used to extract something from the target. Maybe DNA or other bio samples from an organic target or energy, plasma, unobtainum radiation from a mechanical target.
The first scenario for them is they will be used to hold fast a large reptiliod momma while other Space Marines rush the nest to steal her eggs. Each successful hit that holds (auto hit after the first, but a chance to beak hold every lizard turn) reduces big momma's "action points" (for QILS, this temporarily takes away one of her dice.) Why not just kill her? Well, maybe she is just too tough to kill - I could send ten guys and lose five or so to extract or fifty (costing lots of logistics resources) and lose twenty to take her out. Also, killing her might risk breaking the eggs. And leaving her alive means I can come back next laying season for more. Or maybe I just have a moral obejction to ... wait ... never mind that last bit.