Warhammer 40,000: Eternal Crusade / Characters

Tactical Marine

The basic class, able to equip standard weaponry, as well as wield knives.

Jack of All Stats: Is this, having no glaring weaknesses but at the cost of having no great strengths either. However, it is the only class that can equip capture keys, which are needed to take points.
Multi-Ranged Master: Can use standard bolt guns, plasma guns, grav guns, melta guns, and storm Bolters.
Sword and Gun: Given the size of Adeptus Astartes' knives, they fit this. While you can't switch out the knife for other weapons until after playing the game for a while, you can get a piece of wargear early on to up its damage.

The jump infantry class, specializes in mobility and close quarters combat.

Anti-Armor: Can use power weapons to damage vehicles and hit other infantry really hard. These have a slower attack speed than they starting chainsword, though, so surprise is a necessity against other infantry.
Close-Range Combatant: As the only ranged weapons they can equip are a pistol and grenades, they are definitely this
Jet Pack: Uses one.
Multi-Melee Master: Can use chainswords, power swords, power axes, power mauls, and power fists, which were listed in increasing levels of damage.
Multi-Ranged Master: They can als equip bolt pistols, plasma pistols, and grav pistols.
Necessary Drawback: The more damage a melee weapon does, the slower it strikes. For referene, a powerfist will instantly kill another player, but unless that player is caught off guard, hitting them in the first place is a challenge. By contrast, a chainsword needs several hits to down a player, but it is far easier to get those hits in during a duel. Notably, the game itself acknowledges this: it states that Power Fists should be used for destroying foritifications and vehicles, while other melee weapons should be used for dueling.

The Heavy weapons class, can equip heavy weapons.

BFG: The class's gimmick: Devastators can carry the heaviest non-special class weapons in the game.
Long-Range Fighter: Hits like a truck at range, but their slow movement speed makes them very vulnerable to melee.
Mighty Glacier: Far slower than all of the other classes, and will probably get destroyed in melee, but if they can get their guns locked on you, You Are Already Dead.
Multi-Ranged Master: Can wield heavy bolters, plasma cannons, las-cannons, and multi-meltas.
One-Hit KO: While you'll have trouble hitting people with the lascannon, as it's an anti-vehicle weapon, should it actually hit another player, they will be disitengrated.

The medic class, focused on healing, but can still dish out quite a beating.

Carry a Big Stick: The Space Wolf Apothecary Class (called the Wolf Priest), unlike the other Space Marines sub faction apothecaries, can wield a Crozius Arcanum, since they also fulfil the role of chaplains within their chapter.
Chainsaw Good: Can wield chainswords.
Combat Medic: There's no place for non-combatants in this game, so this is a given.
Healing Shiv: The Narthecium Device that this class possess can be used to heal friendly players, or to fight enemies.
Lethal Joke Item: The Narthecium has the lowest damage of any Space Marine melee weapon, but also happens to be the only baseline Space Marine Weapon that is poisonous, and it's fairly easy to find a piece of wargear that increases the amount of poison damage it does.
Multi-Ranged Master: Apothecaries can equip any pistol in the game.
Trick Bomb: Can equip healing grenades. And unlike the Narthecium, said grenades can be used an unlimited number of times.

The fifth class, cannot use the Jump Assault's jet pack, but can use a shield instead.

Luckily, My Shield Will Protect Me: Can equip shields, something Jump Assault cannot do. The trade off is that it takes up the pistol slot when equipped.
Multi-Melee Master: They can wield any of the weapons that Jump Assault can use.