Everyone who yearns for more Half-Life content might take solace (or find frustration) in the fact that more has been created. However, it's also been scrapped. And, at least some of it had the intent of introducing a new tool to go right alongside the revered Gravity Gun.
This information comes from Warren Spector, who did an AMA on reddit today. Spector, who's most well-known for his work on Deus Ex and Epic Mickey, said that when his studio ran into financial troubles, Valve contracted his team to work on an episode of Half-Life. He says that it was to be set in a part of the universe that "hadn't been explored deeply."
While Valve didn't specifically request it, Spector states that his studio developed something called a magnet gun. How it differentiates from the Gravity Gun was left unstated, but Spector comments that "[it] was entirely different than the Gravity Gun. The two would have been super complementary."
Ultimately, the project never came to fruition. Valve went another direction and left the episode -- however complete it may have been -- behind. But, Spector says he'd like the magnet gun to be implemented someday. "I wish [Valve] would do something with the magnet gun. It was fun," he remarked. "We came up with some cool stuff to do with [it]."
We've reached out to Spector for clarification on the mechanics of the magnet gun. If he's able to elaborate, we'll share the details.