Predator Tank
The Rhino Transport has seen more permutations than any other vehicle in the 41st millenium barring the Imperial Guard Chimera, and with good reason - it's that damned versatile. One of several uses for the Rhino involved ripping its troop transport capabilities out entirely, replacing them with ammunition stores, chassis reinforcements, extra armor, and weaponry hardpoints to turn the Rhino into a more conventional tank. The result is the Predator', which has since become the primary battle tank of the Adeptus Astartes. As it was in use extensively during the Great Crusade, you can expect to see it in frequent use with the Traitor Legions as well.
The Predator Tank, being functionally a converted Personnel Carrier, isn't quite the equal of the Imperial Guard Leman Russ in terms of firepower or armor, but makes up for this with superior accuracy, greater flexibility, and cheaper to field than its Imperial Guard counterpart - traits which carry over to the Tabletop game. A Predator can easily be tailored for either an anti-infantry or anti-vehicle role with equal ease, and costs notably less than Leman Russ to outfit - a Predator Destructor can be outfitted for 100 points, whereas an annihilator costs 165 - both being considerably cheaper than a conventional Leman Russ or one of its tank-hunting variants, with better accuracy as part of a bargain.
All in all, the Predator is a decent and surprisingly overlooked vehicle; players tend to eschew it in favor of other heavy support choices available - the Predator takes up a valuable heavy support choice, after all - but make no mistake - the Predator is a potent force that should not be underestimated. Whilst it lacks the ammo-spewing fury of other Imperial tanks, its firepower is nothing to sneer at and its armor is quite good as well - it's hard to find a more efficient vehicle for a heavy support choice for the points-cost involved. An old saying amongst Marine players of both flavors is that if you have the points and a free slot with nothing else to put in it, you can't be let down by the Predator.
Predators are often organized into common variants, for anti-infantry, anti-vehicle, or close assault purposes. These three common variants, dubbed "patterns," by the Adeptus Mechanicus, are listed below:
Destructor Pattern Predator
AKA, the Predator Destructor. The Destructor is armed with a turret-mounted Autocannon and sponson-mounted Heavy Bolters. The most common form of Predator due to its ease of maintenance (and low points-cost), the Destructor offers large amounts of Dakka for a Marine force group, as well as the ability to engage light vehicles with its Autocannon. It lacks, however, the ability to do much damage to enemy heavy vehicles unless it targets vulnerable rear armor with its main gun. Optimized for hunting infantry, the Predator Destructor is a solid choice for an army, though it competes heavily with other heavy support choices for the role.
An efficient and popular modification for the Destructor is to replace the Heavy Bolters with Lascannons, giving the Destructor the ability to reliably engage and destroy vehicular threats, since its main gun is no slouch in the anti-armor despartment. This particular variant is especially popular amongst Chaos Space Marines, who often fit the vehicle with a Havoc Launcher to make up for the loss of anti-infantry punch, resulting in a much more ubiquitous vehicle overall.
Annihilator Pattern Predator
AKA, the Predator Annihilator. Whereas the Destructor pattern Predator is designed for engaging Infantry, the Annihilator is specially-built to destroy vehicular threats. It is equipped with a twin-linked Lascannon in its turret, and a Lascannon each of its sponsons. This optimizes it for a role as a tank-hunter, giving it extensive anti-vehicle punch at a much more reasonable cost than several tanks specialized to this role, such as the Leman Russ Vanquisher. A full volley of Lascannon fire is sure to give a solid punch against enemy armor, as well as the errant high-value independent character.
A common modification for the Predator Annihilator is to replace its Lascannon sponsons with Heavy Bolters. This gives it notably higher anti-infantry punch and has the added benefit of giving the Annihilator the ability to launch some serious hate at enemy units trying to close in, making it extremely popular among the Loyalist Astartes (as well as popular amongst tourneyfags, because it's generally is considered the most-efficient use of points for the thing). Sadly, tanks don't have the option of a weapon that makes up for the loss of anti-vehicle weaponry (since the Hunter-Killer Missile is single-shot, as are combi-weapons), which tends to make it a bit less common.
Baal Pattern Predator
The Predator Baal is unique to the Blood Angels, which is designed specifically for urban combat. As such, many of the weapons it has are designed for clearing out troops in defillade or buildings. The primary armament of the Baal is either a twin-linked Assault Cannon, or a Flamestorm Cannon, which is functionally a bulked-up heavy flamer designed to deal with armored infantry, ideally ones inside bunkers or hiding in forests. Its sponsons, likewise, are designed for urban combat - either Heavy Bolters or Heavy Flamers. The Baal thus excels not only in dealing with troops in cover, but in dealing with large clusters of enemy units, such as Orks or Tyranid swarms.
Sadly, the Baal Pattern is only available to the Blood Angels and their descendant chapters. The Blood Angels were the ones who found the STC (Standard Template Construct) for the design during the Great Crusade, and decided that they liked the design a lot. So in a borderline-heretical move in the eyes of some, the Blood Angels refused to show the specs to the Adeptus Mechanicus, functionally deciding to take their Baal and go home.