Havoc

I am Heavy Weapons Guy, and this is my weapon

Havocs are the Chaos Space Marines' equivalent of Devastators. Like their loyalist counterparts, these guys drag the heavy weapons into battle, laying out copious amounts of fire to support their brethren. Havocs can equip the basic heavy bolter/missile launcher/lascannon options that Devastators can, though you won't be seeing any plasma cannons, multi-meltas, or grav-cannons on your spiky guys. Unlike loyalist marines, Havocs still have access to autocannons that can be lugged around by a single Marine, as well as up-gunned Rotor Cannons. They also like to stick big-ass bayonets on their guns, just in case the opportunity to stab something with an autocannon, heavy bolter or lascannon presents itself. All of them wear the common Chaos Power Armour.

On the Tabletop

Havocs clock in at 13 points each, just like their loyalist counterparts. Outfitted with a Bolter, Bolt Pistol, Frag Grenades and Krak Grenades, up to four Havocs may trade in their Bolters for either a Special or a Heavy Weapon. The list is more limited than the loyalist one, but it does grant access to a neat little list of guns. Bolters let you hit enemies within 24" of the unit without sacrificing firepower, while chainswords provide an extra attack. While this does not seem very meaty, it can prove a nasty surprise for any enemies that seek to assault the Havocs to keep them out of the fight. The champion can hand over his bolter and bolt pistol (so no three pistols like the Devastator sergeant!) to pick two from the pistols and melee weapons list, or take a special weapon. Unless you are planning to take special weapons, doing so is not really worth the price. Sure, a power weapon/plasma pistol combo is fun to play with, but you won't really getting a lot of mileage out of them. The three special weapons are listed below.

• Flamers are, well, flamers. 1d6 auto-hits is nice, especially when you use several against a large blob of infantry. Cheap too and probably the smartest choice for your aspiring champion when it comes to defending the squad.
• Plasma Guns really shine in the new edition. Rapid Fire 1 with S7 AP-3 will really ruin the day of any MEQs you come across, but multi-wound TEQs can prove to be a bit of a problem. Risking death from the supercharged shot is risky and not that rewarding. Useful for adding some anti-heavy infantry support on your champ albeit pricy.
• Meltaguns are meant to melt tanks. S8 AP-4 DD6 will really ruin a tank's day. Not exactly a smart choice for an AC.

Next are the Heavy Weapons. The Champion can't take one of these, but they come with the bonus of being usable at long range.

• Heavy Bolters are your bog standard anti-infantry weapon guns. The full set nets you 12 shots at S5 AP-1 and new for 9th edition, damage has been upgraded to 2! Do note that most Heavy Bolters you'll have will be on tanks, who get -1 to hit often because they move around a lot. Only a fraction of the cost of the other guns, so if you need them this is the place to go.
• Reaper Autocannons have become less useful against one of their primary targets in 8th edition: light and medium tanks. Sure, the S7 still has a decent chance to cause damage, but the AP-1 will really hamper their effectiveness against good saves so the D2 won't be able to do its thing. Still, a full squad gets 8 shots with the things, so you can look at getting at least a few wounds in. Monsters with high Toughness but average saves (aka most Tyranid gribblies) are often better picks, so choose your targets wisely.
• Missile Launchers are expensive (100 for a set), but they make up for it in versatility. Frag missiles let you take huge chunks out of blobs, while the second shot is a poor man's Lascannon. This means that you'll always have the proper response to a target, and at a decent range to boot.
• Lascannons carry potent tank popping abilities. They render armor saves a formality and can deal crippling damage against tanks in the most average of circumstances. You'll pay through the nose for this right though, so keep them safe.
• Reaper Chaincannon are the new kid on the block with Games Workshop's new Chaos expansion. Sort of. It's literally just a bigger, beefier, and spikier Proteus pattern Rotor Cannon from the Heresy, but hey, it sure as hell gets the job done. This is a pretty good way of BRRRTing your way through most MEQs and lower, with 8 shots at strength 5 and AP-1 but it does only have a 24" range.

Havocs have access to Chaos Icons, but aside form the Icon of Vengeance these are circumstantial at best. They can also pick one of the Legion Traits. The Renegade, World Eaters, Emperor's Children and Night Lords ones are not all that useful. The Word Bearers grant a re-roll on Leadership, which is handy to make sure you don't lose yet another of your big guns. The Black Legion one is useful only if you're equipping them with Plasma Guns. No, where they really shine is with the Iron Warriors and Alpha Legion ones. The Iron Warriors let you ignore cover bonuses and gives rerolls to wound against buildings. The former is incredibly useful against anything in cover, while the latter ability is useful against any fortifications your opponent brings to bear, as long as you bring the big guns. The Alpha Legion's ability gives a -1 to hit when targeting your unit from more than 12" away. This is spectacular: Havocs are fragile enough as is, so being more difficult to hit is all but mandatory to stay alive.

And then the Vigilus Campaign happened

Eventually, GeeDubs agreed that the Havocs were shit, and so Havocs were massively revamped during the Vigilus Campaign. First off, the bad - they had a small points increase, everyone but the Champion can no longer carry Special Weapons, and the size of the unit can no longer be increased with fodder Marines. However, Havocs were made to distinguish themselves from their Chosen compatriots in other ways. For starters, they were boosted to Toughness 5. They also inherited the ability to ignore the to hit modifier for moving and shooting with Heavy Weapons, meaning they're no longer sitting still all game waiting to be shot at - and since all they can carry now are Heavy weapons, it's something they needed to stay viable. In short, there are now legitimate reasons to take Havocs over Chosen if you want some cheap big guns. Oh, and they got a new gun in the form of the aforementioned Reaper Chaincannon. Because it apparently took the Traitor Legions 10,000 years to come up with the idea to upgrade their old Rotor Cannons to shoot Heavy Bolter size bullets.