Everyone is quite familiar with the “normal” Riptide as one of the (now) iconic Tau units, but I think many players are not as familiar with the R’varna variant offered by Forgeworld:
The R’varna has the basic same stats/5++ save as a normal Riptide, but gains +1T/+1W (so T7 and 6W, respectively). It also loses Jump Pack Monstrous Creature (it is just a “normal” MC) and has a different variation of Nova Reactor (can choose to gain a 3++, set off a 6″ EMP “nova” around itself, gain Fleet and run 2D6″ for a turn, or shoots its weapons twice at the cost of not shooting next turn). It can also take up to two Missile Drones (just like normal Riptide) and is limited in Wargear to taking a Positional Relay and/or a Stimulant Injector.
What really makes the R’varna stand out, though, is its unique weapon systems: two pulse submunition cannons. These each shoot a S6 AP4 Large Blast out to 60″ and have the Cluster Fire rule, as follows:
“Cluster Fire: Very Bulky models, as well as those with the Bike/Jetbike/Beasts/ Cavalry type, suffer two hits each from this weapon at an increased Strength of 7. Extremely Bulky and Artillery/Monstrous Creature/Flying Monstrous Creature/Vehicle (any type) models and specifically targeted buildings and fortifications suffer 3 hits each if they are hit by the weapon at an increased Strength of 8.”
So, basically, the R’varna is particularly effective at dealing with hordes (up to 4 x S6 AP4 Large Blasts a turn, which can Ignore Cover with marker light support), with massed bike/cavalry armies, and with massed light-medium vehicles (i.e. like a MSU Space Marine Battle Company with tons of free Rhinos/Razorbacks). In particular, the R’varna’s ability to inflict 3 x S8 hits per vehicle struck by its pulse submunition cannon blasts gives its the capacity to reliably take out AV12 and lower transports on a highly efficient basis especially given its tremendous range and staying power.
Finally, with its high toughness and wounds and ability to get FNP from Stimulant Injector, the R’varna can be an excellent “meatshield” unit to absorb the enemy attention and shooting away from the rest of the army. For example, a BS4 Plasma gun would take 6-7 shots to cause a single unsaved wound (or about 41 shots to kill the R’varna outright), while a BS4 Krak Missile Launcher would take about 20 shots to cause an unsaved wound (or about 120 shots to kill it outright). Even in close combat, the R’varna has 3 x S6 AP2 attacks, so it is not completely helpless if charged and it high T7 means that even PFs are only wounding it on a 3+ (and almost everything else is wounding it on a 6+).
The biggest threat to a R’varna is, naturally, Grav Weapons, since they ignore its high Toughness. If the rest of your army can deal with the Grav threat effectively, then the R’varna should be able to operate with high resiliency and effectiveness all game long.