-=Zerg on Island Maps=-
*Can research Burrow for Drones to avoid enemy drops.
*Can research Burrow for Hydralisks on Island Maps for unburrowing and surprising enemy Shuttle Drops.
*Multiple Nydus Canals are required in the late game on Island Maps.
* Dark Swarm helps dramatically while attacking Islands.
*Plague is good against Capital Ships.
*Zergs can Parasite Dropships and Shuttles or expensive enemy units the enemy is less likely to suicide.
*Ensnare helps chase down Wraiths and Corsairs. You can Ensnare those units and then run-by them and go do your drop. You can also ensnare Carriers and Battle Cruisers to chase them down. Ensnare also negates Marine's Stim Pack's effects. Ensnare is very good in conjunction with Lurker drops when dropping enemy worker lines.
You may want Queens and Spawn Broodlings if you are against High Templars with Psionic Storm.
*If a Zerg goes mass Mutalisks versus a Protoss, if he can make it to Hive Tech, Devourers should help significantly in beating Corsairs. In fact, Devourers may make Corsairs obsolete altogether since Devourers are so effective.
*Zergs need to double expand in the early game to hold their own with gas. Kind of like Sauron Zerg mass expansion style.
*Hydralisk + 1 attack upgrade should be preferred over +1 defense for intercepting enemy drops.
*You may want to send Drones early to potential future expos, and then burrow them there, since it may be difficult in getting Overlords (with drones) there later.
*In ZvP, two Lair Hydralisk Drop rush is a viable strategy. (Nicknamed "Twin Lairs") A second Lair will give you a time advantage where you get both Overlord upgrades quicker and can expand quicker. A second Lair only costs 100 extra gas but allows for a quicker first expansion. On maps like Halls of Valhalla, Dire Straits, and Island Hop, where slow drop expand isn't an option, two Lairs may be a better option.
*In ZvT, again a two Lair Lurker drop rush is a viable strategy. (Nicknamed "Twin Lairs") A second Lair will give you a time advantage where you get both Overlord upgrades quicker and can expand quicker. A second Lair only costs 100 extra gas but allows for a quicker first expansion. On maps like Halls of Valhalla, Dire Straits, and Island Hop, where slow drop expand isn't an option, two Lairs may be a better option. BESIDES, Lurkers are good against a Terran who goes Wraith because the Terran foregoes an Academy+Comsat Scanner.
*One opening possibility for Zerg is to make both a Hydralisk Den and Spire. The Spire is only for four or so Scourges to scourge Shuttles and maybe Corsairs, while the Hydra Den is for Hydralisks to counter any possible Zealot drop.
*Excess minerals can be spent on an extra Sunken or Spore Colony to slow down Zealot or Reaver drops or Marines & Medics, Goliaths, Vultures, or Wraiths.
*Hydra Range first before Hydra Speed will help better defend against Corsairs. This will allow your overlords and overlord drops to stay alive longer.
*If you have say 20 Scourges versus 4 Battle Cruisers, the proper way to micro is to do the "Divine Wind" method: One group of four scourges are sent ahead to get one-shot killed, while four groups of four Scourges all are split and kill one Battle Cruiser each. On Island Maps, Zergs with mass expansions can pump mass scourges.
*Knowing how to Doom Drop is important.
*Reavers excell in not only killing drones but also expansion Hatcheries when the attack upgrade is done, which changes from 25 to 125 damage.
*Queens & Devourers vs. Protoss air is a crazy-good combination. Ensnare can allow you to chase down the enemy units. Ensnare reduces the rate of fire of Corsairs by 10%. Any Interceptors Ensnared won't attack. Each Devourer's Acid Spore increases a unit's cooldown by 12.5% while also for each Acid Spore the unit takes one extra damage per attack. Finally a few Devourers at 250 health may be used with Overlord sight upgrade to snipe enemy Observers while your Lurkers rampage.
-=Terran on Island Maps=-
*Old school Goliath Drops with +1 attack upgrade for use against enemy drops.
*In TvZ, maybe always make at least one wraith for scouting and harassing. The Starport will be needed for mass Dropships eventually anyways.
*In TvP, mid to late game, a Terran may want some Wraiths to attack-move chase down Shuttles. In the early game, they would be killed by Dragoons. Also, Wraiths can snipe enemy Observers to kill Carriers while Cloaked.
*In TvP, if both players are equal, the game will progress to massive air on air battles with victory fleets. The Protoss won't be able to break-into the Terran without Carriers. One Terran might turtle with abundant cheap Turrets, ranged Goliaths, Spider Mines, and Sieg Tanks. The Protoss might turtle with ranged Dragoons and other tech surrounding his base's periphery.
*In TvZ, two Starport Wraiths is a very viable strategy which will give you air dominance and also give you map control on Islands where scouting is more difficult. Wraith micro wasn't as refined back in 2005 when Island Maps were last played. Two Starport Wraiths would of course be followed up with Two Starport Dropships with mass Marines & Medics.
*In TvZ, Mechanical play may be worse than Bionic play because Hydralisks do increased explosive damage against Mech units.
*Terrans may want to lay Spider Mines where they think the enemy will drop or recall at. They may place Spider Mines near Turrets incase a Turret luckily kills a Shuttle and the Shuttle unloads units shortly before dying.
*Maybe twin academies (two academies) for rushing super fast Marine Range and Marine Stimpack would be fun to try.
*Knowing how to Dropship micro is important.
*In TvP, because you are map blind in the early game of an Island Map, you may want to make a fast Academy + Comsat Scanner + small Bionic force in the early game.
-=Protoss on Island Maps=-
*Old school four Zealot Drop rush is a possibility.
*You can Hallucinate Arbiters for Recall.
*Maybe can make shield Batteries for use with harassing using Reavers, Shuttles, and Corsairs since one has to make due with less gas intensive units on Island Maps.
*Several observers should be made since less scouting can be done on Island Maps.
*Arbiter's Recall ability, possibly with Hallucinated Arbiters, remains a possibility. If it is a small island, a player may attempt to use his workers to partially block the recall by pulling the workers away from a worker line to intercept the recall.
*In PvZ, the main build order possibilities are Reaver/Corsair or Robo/HT & DT/Corsair.
*In PvT, if both players are equal, the game will progress to massive air on air battles with victory fleets. The Protoss won't be able to break-into the Terran without Carriers. One Terran might turtle with abundant cheap Turrets, ranged Goliaths, Spider Mines, and Sieg Tanks. The Protoss might turtle with ranged Dragoons and other tech surrounding his base's periphery.
*Knowing how to Shuttle micro is important.
*A Protoss player may use excess minerals to make a couple Photon Cannons to slow down enemy drops.
*In PvZ, if you have a mass of Corsairs, you might as well researcha nd use D-Web when dropping or defending.