Command & Conquer 3: Tiberium Wars/Neutral buildings

Tiberium spikes
Tiberium Spikes are found in a few battlefields. They provide a burst of money (typically around 500) and a steady stream (15 or 25, depending on the game version) of income every few seconds afterwards. Since more money is never a bad thing, capturing Tiberium spikes early will help you reap free rewards from them. Keeping in mind a $500 engineer is required to obtain a spike, ensure that you're able to hold the spike long enough for you to recover your 500; otherwise, it's a losing proposition.

At any rate, most build orders have the construction of a Barracks, Hand of Nod, or Portal second so that players can produce engineers, saboteurs, or assimilators and capture Tib spikes early.

Destroying a Tib spike spawns a small patch of green tiberium at its base.

Expansion point
Expansion points, when captured, act like outposts. They give you ground control over the surrounding area, allowing you to build a base up around them. It is often best to capture one when you have several base defences queued up so you can defend your investment. More often than not these are set up near Tib fields, so you may want to capture an expansion point with a refinery queued up, too.

Reinforcement Bay
Reinforcement bays do not often appear in multiplayer, but instead often in the single player campaign. It is a very good idea to capture these whether in single player or multiplayer, because they give units to the player that captures them.

Subway Hub & Entrances
Capturing a Subway hub automatically puts all Subway entrances under your control. The subway entrances have three garrison spots for (most) infantry, but these garrison slots are shared by all subway entrances on the map. Essentially, while you control the hub, any and all entrances will provide an instantaneous transport for practically any infantry unit. This can be a nasty shock to a player who has been skimping on his or her anti-infantry development, especially at an odd angle.

Once the hub is captured, it does nothing, but if the hub is captured by an enemy engineer, all entrances change allegiance. Therefore it can be prudent to, once you've captured the hub, destroy it so that the enemy will be unable to claim the entrances for him or herself, and will have to resort to destroying them.

EMP Control Centre
The EMP Control Centre gives you access to a powerful EMP strike every few minutes, shutting down vehicles and structures in its radius. It covers an extremely large area, and is the only EMP attack in the game that can hit aerial units. Hitting an aerial unit with an EMP requires unparalleled accuracy, but a successful hit will shut off an aircraft's engines, causing it to be destroyed on impact. Any aircraft is vulnerable - from Orcas to Devastators and even Planetary Assault Carriers; however, be sure the Devs and PACs in particular lack shielding, otherwise the EMP will be absorbed by the shields.

Regardless, the EMP Control Centre is a powerful piece of technology that can seriously hamper an attack or allow an attacking force to march right past advanced base defences, making it extremely contested. If you can't hold the EMP, destroy it to prevent its use against you.

Mutant Hovel
A common neutral structure that allows you to recruit Mutant Marauders. They are cheap and quite effective against both infantry and aircraft, but they are not often used due to their slow size and ineffectiveness against larger, more powerful targets.

Defensive Turret
This turret is a powerful cannon that can repel all but the most dedicated land attacks in an area around it. It is quite effective against single infantry, to the point where a single engineer sent at a turret will fail at capturing it. Turrets are quite sturdy but not invincible, and are often destroyed by an aerial attack.

Defensive turrets do, however, have a minimum range, and cannot attack units that are right next to it. GDI and Nod players therefore can use Call for Transport to land an Engineer within the turret's minimum range, easily allowing for its capture.

Tiberium Silo
This silo gives a large burst of money to the first player that captures it. It otherwise is completely useless, and capturing it again will not yield any rewards.