How to build an harpoon innate attack?

Question

I'm putting together a GURPS character as a PC option for my players. The idea is that it's a heavy lifting robot that gained sentience when an AI took it over, but is limited to its current form. It is tentatively named "CARL-3".

CARL-3 has an innate attack - he can shoot a harpoon-like dart from each "arm" that is attached to a winch, and use it to reel or tow objects, or haul himself into difficult spaces (he's got tracks, instead of legs).

I've got a lot of advantages/disadvantages figured out already for his chassis, but I'm having a hard time with the harpoon attack.

Obviously, he'll have Innate Attack (Impaling) at at least 1 level, which defaults to a ranged attack. There are tons of afflictions and stuff that I could apply to that, but I'm having a hard time figuring out something that would essentially work like the harpoon equipment item works - it prevents something from moving away if it fails a ST contest. Binding seems like it does more than I need - he can't root somebody in place like Spiderman, but he can spear them and haul them closer like Scorpion from Mortal Kombat.

Since it isn't just an attack, but also works on objects, and lets CARL-3 lift himself, I might need to tack on other advantages as well. I'm trying to keep CARL-3's point total below 200, which isn't impossible-seeming since he has a ton of disadvantages (horizontal, no fine manipulators, no sense of humor, etc), so I'd prefer to try to keep the point cost of this ability below 50. I'm the DM, so I have plenty of leeway if that isn't possible.

What's the best way to build this ability?

Answer 1

This is a classic case for an Alternative Ability set, described on p11 of GURPS Powers. The way those work is that you have a group of associated abilities, of which you can only use one at a time. For this one, those abilities seem to be:

• Ranged impaling attack.
• Binding.
• A very limited form of Flight.

To buy this set of abilities, you price them up separately, then buy the most expensive one at full price, and pay 1/5th price for each of the others.

This discount comes with some restrictions:

• Switching between the abilities requires a Ready manoeuvre.
• Anything that disables one of them disables them all - the obvious example here is the line breaking.
• If any of the abilities can't be activated again until its duration expires, then none of the abilities are available for the duration.

If this makes sense to you, I'll happily help you with the design, but I'll need some more details first.

Answer 2

For pulling the target towards you, the closest official way to do it is to apply the Retractable enhancement to Binding (found on page 30 of Pyramid #3/115: Technomancer). The Binding should be Linked to your attack (alternatively, there's some argument for allowing Follow-Up on the Binding in this case, but it's a step outside intended use that provides relatively little gain).