Whilst Tau infantry and battlesuits are effective, Tau vehicles are some of their star performers. Maneuverable thanks to the Skimmer special rule and bristling with weaponry, you definitely don't want to leave them at home! The Skimmer rule does raise the question of how to base appropriately. I've found it best to prop mine up on bits of cocktail stick- a cheap and effective method of creating an impression of hovering just above the ground.
I almost always run my Fire Warrior Cadres with Devilfish transports. They provide flexibility, mobility and portable cover for their passengers. Their Seeker Missiles add organic AT capability to Fire Warrior Cadres, and mean that they can sit at the back of the board on overwatch to hit out at enemy armour before rushing the cadre forwards in later turns. Combined with Pathfinders or a Skyray for organic Markerlight coverage, those Seeker Missiles are a very useful!
I use Brigade Models M58 Sugama APC for my devilfish. For some variation you could also use the Wiranto Command APC, although it's an option I've not used.
Tetra & Piranha
Tau recon skimmer formations are a popular choice for providing cheap Markerlight coverage and adding to your activation count. They also have some flexibility, thanks to being able to freely mix Tetra and Piranha in the same formation, for some interesting combinations.
I use Brigade Models R35 Bhima Armoured Car for my Piranha. For my Tetra I use the same machine gun which comes with the APCs- Brigade Models were happy to swap out some of the normal turrets for machine guns, just shoot them an email!
The Skyray serves 2 purposes, and does them both very well. Whilst their main purpose is to keep the skies clear of enemy aircraft, I generally find myself actually using Skyrays to extend my Markerlight coverage. This, combined with 2 Seeker Missiles and a Smart Missile System makes them well worth the 100 points. However, with a 5+ save, you do need to be careful where you leave them to stop them from being picked off.
Another simple weapon swap conversion like the Tetra, I use Brigade Models P147 Arjuna AA Vehicle with the turret swapped out for the missiles from the Katiusza MRL. This works well as the Arjuna is clearly based on the Sugama chassis, a visual reminder that the Skyray has the same save as the Devilfish in game.
The Tau MBT is excellent, and comes in 3 different flavours (5 in the Xar'Ka armoured list!). All have the same basic chassis, with 30cm Skimmer move and Seeker Missiles in addition to their other 2 weapons. This again allows them to sit at arms reach peppering the enemy with Seeker Missiles and then jumping forward when the time comes. Not overly survivable, a 4+ save on an Armoured Vehicle is still respectable. Nevertheless I find it's best to take the upgraded formation of 6 Hammerheads to add some ability to soak blast markers. You can theoretically have 4 of one type of Hammerhead and up to 2 of another variant in the same formation, although I'm not sure why you would ever do so. In vanilla Tau you can also add up to 2 Hammerheads to a Fire Warrior Cadre, adding yet more firepower to the cadre; in Xar'ka the Mechanised Cadre is similar, with 2 Hammerheads mixed in with a Skyray and 4 Fire Warrior units mounted in 2 Devilfish.
The star of the Hammerhead show, Railheads can through out a disgusting amount of AT firepower, with a 75cm, AT4+ Lance main gun, supplemented by their Seeker Missiles. Whilst capable of taking down infantry with Rail Gun and Burst Cannons, Railheads are best put to use deleting opposing armour and war engines from across the board.
I use the Brigade Models T14E3 Anjalika MBT for my Railheads.
Were the Railhead is a long range instrument, the Fusionhead is for when you really need to kill something and don't care about getting to close. Fusionheads a particularly useful in vanilla Tau, which has less access to macro weapons than the NetEA Vior'la list. They are also a bit more generalist than Railheads. Whilst a barrage of Seeker Missiles followed up by 6 Twin Fusion Cannon shots can make short work of most war engines, their secondary Smart Missile System is longer ranged than the Railheads Burst Cannons, and have Ignore Cover. Plus, at the end of the day, MW4+ works even better on squishy infantry than it does Reinforced Armour war engines! Add a Skyray for organic Markerlight support and watch your opponents face drop.
I use the Brigade Models T14 Suharto MBT for my Fusionheads. The turrets are actually significantly different from those of the Anjalika, and I've painted the tips of the barrels white to aid tabletop identification.
The unloved child of the Hammerhead family, the Ionhead plays second fiddle to big brother Railhead. The Ionhead does still have its uses. Firstly, if you're short on points, a formation of 6 Ionheads is 50 points cheaper than a formation of 6 Railheads. Secondly, the Ionhead has a definite advantage in the infantry killing business over the Railhead, without the short range of the Fusionhead. I must confess that I haven't used a full formation of Ionheads, but as an upgrade to a Fire Warrior Cadre in vanilla Tau they add the useful ability to shoot beyond 30cm without having to rely on Markerlight coverage to use Seeker Missiles, reaching out and putting blast markers on infantry and vehicles.
The only conversion job among my Tau armour more advanced than a weapon swap, my Ionheads are based on the Anjalika (same as the Railheads), with the weapon snipped off, the turret flipped around and the weapon from the leftover Arjuna turret glued in place.
That's it for vehicles. Next, onto the elite of the Fire Caste- Battlesuits!
Devilfish- M58 Sugama APC and Wiranto Command APC
Piranha- R35 Bhima Armoured Car
Tetra- R35 Bhima Armoured Car with machine gun from M58 Sugama APC
Skyray- P147 Arjuna AA Vehicle with missile turret from Katiusza MRL
Railhead- T14E3Anjalika MBT
Fusionhead- T14 Suharto MBT
Ionhead- T14E3Anjalika MBT with gun from P147 Arjuna AA Vehicle