The Riftbreaker

These items are all in the Alien and Weapons and Equipment research trees (multiple Laboratories and Communications Hubs speed up the research for each, respectively, but Labs are very expensive and consume crazy amounts of energy).

Here’s the available options (they all look like little canister Grenade icons on the research trees) :
Instant Repair (starting)
Small Mine (starting)
Radar Pulse
Grenade
Emergency Explosion
Nuclear Mine
Sentry Gun
Cryogenic Mine
Gravity Grenade

That’s only one to spare as far as I can tell. There’s also something called Time Warp, but I couldn’t figure out where or how it equipped (Gravity Grenade also seems wonky as the Extreme version is Purple and not Red but you can still equip it). As soon as you fill that final slot this pops.