Avenger Strike Fighter
The Avenger Strike Fighter is an Imperial Navy close-range ground-attack aircraft meant for destroying armor and other heavy targets. It does this with the Avenger Bolt Cannon, the Strength 6 AP 3 Heavy 7 gun around which the flyer was built (also called the "Fuck Marines gun" because it ignores their power armor save and wounds them on a 2+), as well as 2 lascannons and 2 hardpoints that can mount anti-infantry or anti-vehicle weapons. Since it was supposedly used a lot by Sebastian Thor's forces during the Age of Apostasy, the Sisters of Battle see it as an instrument of divine vengeance (through superior firepower), so they use it a lot.
The Avenger model is produced by Forge World, released to coincide with Imperial Armour Aeronautica (the book containing the rules for it and other flyers, what with Warhammer 40,000 6th edition having flyer rules).
Forge World was very obviously inspired by the real-world A-10 Thunderbolt II (or "Warthog"), a ground-attack aircraft built around the tremendously powerful GAU-8/A Avenger Gatling cannon. It shoots 30mm depleted uranium shells so fast that it doesn't go "Dakka," it goes BRRRRRRT.
While A-10 whose cannon is like a death ray against tanks due to being able to hit vulnerable roof armour (30mm rounds, even made of highly dense uranium just don't have the mass to punch through front or side), this one's gatling cannon isn't all that great against battle tanks and similar because 40k game mechanics doesn't support roof armor values - just like modern ones ones almost all 40k tanks (except siege ones) would be AV10-11 from the top, and therefore quite vulnerable to the hail of S6 shots. That said, with the Strafing Run and Tank Hunter rules (the latter available only in the Horus Heresy version), it's Gatling gun is actually quite effective against AV 10 or 11 targets. Taking anti armor hard points though allows you flexablity as you use the big gun for anti infantry while the hard points take out armor.