As I continue to look at the leaked rumors about Codex: Genestealer Cults, here are some things that jump out to me from a competitive gameplay perspective:
 Leman Russ variants — Now that Genestealer Cults are confirmed as having access to Leman Russ Battle Tanks (well, all variants except Demolishers, Punishers, and Executioners, it seems), this opens up a whole range of possibilities for them and, especially, for Tyranid allies. Whether armed with the traditional Battle Cannon (S8 AP3 Large Blast), Vanquisher Battle Cannon (S8 AP2 Armourbane), Eradicator Nova Cannon (S6 AP4, Large Blast, Ignore Cover), or Exterminator Autocannon (S7 AP4 Heavy 4, Twin-Linked), plus the options for Lascannon, Heavy Bolter, Heavy Flamer, Multi-melta, and/or Plasma Cannon Hull and Sponson weapons, these Leman Russes add amazing long-range versatility and “heavy firebase” capacity to otherwise close-ranged focuses armies like Tyranids and Genestealer Cults. Imagine having 2-4 Leman Russ variants, screened from enemy assault and melta weapons by swarms of cheap Gaunts and Neophytes, and backed up by powerful close combatant units like Hive Tyrants, Patriarchs, Purestrain Genestealers, and Carnifex broods… the Leman Russes can provide the shooting and even form an “armored shield” for the other units to shelter behind as they advance, then the swarms and “big-hitters” can jump out from behind the tanks and charge the enemy line once they get close enough for assault. Overall, I am quite excited about the possibilities of combining Tyranid swarming/close combat abilities with “Imperial Guard-like” armored firepower like this!
 Goliath Truck — While this cannot be used by the Patriarch, Purestrain Genestealers, or allied Tyranids units (based on the assumption that they will be Allies of Convenience), the Goliath provides the Genestealer Cults with a very versatile transport that has some supporting firepower of its own (Autocannon and Heavy Stubber), can hold up to 10 passengers, and, most importantly, is Open-Topped. This means that all 10 passengers can shoot their weapons and/or assault after they disembark. Combine this with the Neophyte Hybrid, Acolyte Hybrid, Metamorphs, and Aberrant infantry types available to Genestealer Cults, plus the new shooting weapons (like the man-portable, 24″ S9 AP2 Heavy 1, Mining Laser) and close combat weapons (like the Heavy Rock Drill, Heavy Rock Saw, and Heavy Rock Cutters, all of which are basically PFs with additional bonus rules), and you have very flexible, tactically capable options for the Genestealer Cult and their Tyranid allies, especially when deployed via the Goliath Truck for additional protection, mobility, and supporting firepower.
 Goliath Rockgrinder — The “heavy” variant of the Goliath Truck, this vehicle can only carry 6 passengers (they can still all shoot, though) and loses the Open-Topped rule, but gains better front armor, the special Drilldozer Blade wargear (ignore Dangerous Terrain and significantly enhanced Ram and Tank Shock abilities), and several useful weapons options. It starts with a Heavy Mining Laser (36″ S9 AP2 Heavy 1) in place of the TLed Autocannon on the regular Goliath, but can choose to upgrade this to a Clearance Incinerator (Template S5 AP4 Torrent… so basically a Heavy Flamer with the Torrent rule, which is very good) or the Heavy Seismic Cannon (at 0-12″ S8 AP3 Heavy 3, at 12-24″ S5 AP4 Heavy 6; both profiles count any to Wound/to Penetrate roll of 6 as AP1, so quite versatile overall). Additionally, the Goliath Rockgrinder can take the “Cache of Demo Charges” upgrade, which gives it a 6″ S8 AP2 Large Blast that can be used every turn, unlike normal Demo Charges, which are One Use Only. Finally, since Goliath Rockgrinders can be taken in squadrons of 1-3, you can put all of this firepower together and “triple” it if you want in a single FOC slot, making for some very potent damage output (imagine hitting an enemy unit with 3 x Clearance Incinerator templates followed by 3 x Demo Charges at close range, or hunting tanks/MCs with 3 x Heavy Mining Lasers plus additional models shooting “regular” Mining Lasers (same as the heavy variant, but with 24″ range vice 36″ range) while embarked inside the Goliath Rockgrinders? As you can see, there are lots of possibilities for this very flexible vehicle, especially combined with the Genestealer Cult infantry options and other vehicles like Leman Russes, Chimeras, Sentinels, and “vanilla” Goliath transports.