Alternate Spy Watch: some kind of high-precision digital timepiece, named after some pun on synchronization. Instead of turning the user invisible, turns one ally invisible, for seven or eight seconds. Any action dispels the cloak, possibly excepting detonating stickies; if the action requires a warmup, such as a Heavy spinning up, the warmup can happen during the decloak. Once the ally uses the cloak, the Spy's cloak meter is drained fully, and it cannot be refilled until the ally is visible once more. The cloak provides no damage reduction, and it ripples when the ally is shot.
Alternate Spy Watch: Alarming Clock. Not really serious about this, just wanted to use the name. Charges more slowly than the default watch. Makes a horribly loud noise while active, disabling the cloaks and disguises of all enemy Spies within approximately Buff Banner range, as well as disrupting the cloak and disguise of the user. In appearance it is an egg timer duct-taped to the Spy's wrist.
Sentry replacement: laser tether. Has a big dish or radome on it. Once deployed, the building projects a laser beam in a straight line to the Engineer it belongs to, though it is stopped by walls. Any enemy intersecting the beam takes damage; the farther the Engineer is from the building (that is, the longer the beam), the more damage it does. Unlimited range. While sapped, it changes teams, with the tether instead tracking the Spy who planted the sapper. Has a smaller hitbox than a sentry, and projects the laser from the widest part, so that anyone capable of shooting the building can in turn be burnt by it, at least in theory.
Sentry replacement: stealth turret. Similar to an ordinary sentry; it is smaller, faster to build and upgrade, but it does less damage, tracks more slowly, and has less health and a shorter range. It also does not beep when on standby. This sentry conceals itself in a covered hole when there are no enemies present. When firing, deploying, upgrading, or being sapped, it is above ground; at all other times it goes back in its hole. While underground, it takes drastically reduced damage from all sources, possibly excepting the Homewrecker.