Yep, I love the Picadore.
I thought up an alternative version of a goblin ridding on the back of a giant frog, which uses it's sticky tongue to make similar "harpoon" attacks on single opponents. I haven't statted it out yet, but the idea is there.
Regarding the Harpoon... I don't imagine it as a simple spear with a single point. I imagine it more of a spear with large barbs and hooks on it. Even if the spear point "misses" the target, all the hooks and barbs will still catch on the target's clothing, armor, and shield. This allows the DM to describe why a characters is "hooked" without them actually being impaled on a spear.