WARNING: The following contains spoilers for Iron Man 2020 #3, by Dan Slott, Christos Gage, Pete Woods and VC's Joe Caramagna, on sale now.
Possibly the most intriguing aspect of the Iron Man character, in any incarnation, is ingenuity. The very origin of the character in most instances comes from a cobbling together of simple resources and the right circumstances or cause. While Iron Man is often defined by his armor and its protective capabilities, he often finds himself in events where he needs to take the offensive.
The most common weaponry displayed by Iron Man is his famous Repulsors. The multi-purpose technology within allows him to fire off bursts of energy or assist in the propulsion of the suit during flight. Another of his famous attacks involved discharging a large amount of power from the arc reactor on his chest -- this is commonly referred to in its base form as the Unibeam.
It's also important to remember that the suits are made of metals and alloys, so even a regular old punch from Stark hurts. However, this is standard stuff in the world of superheroes. When the ingenuity of Iron Man meets offensive capability, his attacks can get rough. In Iron Man 2020 #3, Arno Stark uses the gears around his shoulder pads to bear hug Tony's copy and then grind him down to nothing. It's not the strangest armor attack Iron Man has ever used, though.
Density Change
Tony has been experimental with his armor and its attacks. The Model 19 armor, a.k.a. S.K.I.N. due to its liquid metal sections, had token gold areas of malleable metal that could be manipulated. Unfortunately for Stark, this suit was destroyed by the villainous Ultron. While active, however, the suit allowed for redistribution of density, which has also been used in other suits since, including his Superior Iron Man suit.
Using the changes in density, Iron Man was able to augment his attacks, put more power behind his punches, lighten his limbs for more nimble strikes, and even make himself heavier to anchor himself down or overpower foes. Though not an attack in itself without physical exertion, the density manipulation of the Model 19 allowed for tactical changes on the fly.
Puppeteer and Envelope Others
Following an event known as AXIS, Tony's morality was swapped along with other heroes and villains. What's worse is when this issue was seemingly fixed, the evil Stark found a way to shield himself and continue his descent into villainy. While the morally bankrupt version of himself ran amok, creating apps that manipulated the psyche of the general public and even throwing Daredevil off of a building, he continued his vindictive methods in the very armor he crafted.
As the dastardly Superior Iron Man, Stark attacked his foes in underhanded ways. Modeling his newest armor on the Venom symbiote, he removed the susceptibility to sonic waves. As he was bonded to the suit in the same way one is traditionally bonded to a symbiote, he could order the suit to do his bidding. This included enveloping others and forcing them to move as the suit moves. Not only that, but the liquid-metal nature of the suit allowed him to smother those trapped inside. It was a truly disturbing period in the legacy of Iron Man.
Anti-Elf Touch
Malekith, by nature, is an annoyance to everyone he comes across, though it's usually Thor he butts heads with. He raised the ire of Iron Man when he attempted to steal several powerful magical rings, formerly used by one of Stark's greatest enemies, The Mandarin. Tony tried to retrieve the rings but his attempts at a quick, stealthy retrieval were met with issues. For his next attempt to get the rings out of Malekith the Accursed's hands, Tony needed to get more specific.
Rather than creating a suit to do a whole host of things at once, he decided to make his new armor exclusively to defeat elves. He used Cold Steel -- which is extremely harmful to the species -- and thus became untouchable. Malekith leans on magical attacks, which Cold Steel also repels. Tony was able to take back the rings with little effort after that and return them to a safe location.
Ice Beam
The Avengers aren't in the business of killing their enemies, so Tony has become adept at developing an array of non-lethal pacification methods. Using his knowledge as a former developer of actual weapons, Tony found more ethical means of combat during his tenure as Iron Man. One of the strangest is his ability to project a beam of ice -- sometimes referred to as the Freeze Beam -- to temporarily stop his adversaries.
The beam of ice isn't organic or magical -- it's just science. Tony emits a concentrated blast of Ultra-Freon energy from his chest reactor, much in the same way his Unibeam is fired.
Bottled Lightning
In the alternate universe Marvel 1602, Iron Man -- referring to himself as Lord Iron -- makes a suit by trapping lightning in bottles to power his offensive capabilities. Harnessing bottled lightning does amazing things for Lord Iron, even making him invulnerable. In terms of attacks, this lightning imbued him with increased strength and an array of electric weaponry.
Although most entries on this list were invented by Tony Stark, the newest Iron Man seems to be continuing the trend of unique attacks. Arno Stark has a more pragmatic approach to being Iron Man, which is already making waves through the worlds of man and machine. His innovation likely won't stop with shoulder gears.