From the perspective of high level void/infested play (lv60+ enemies) Great ammo-efficient all-range all-around lategame weapons:
Latron Prime/Wraith : unsurpassed burst damage if you can land headshots, decent sustained damage out to mid range, high status.
Quanta : massive aoe burst from altfire aoe headshots, unlimited ammo sustain on primary fire, 50m range.
Amprex : some of the highest real dps in the game, damage chains from every target hit to nearby mods. highly ammo-inefficient.
Synapse : single-target, slower firing amprex.
Burston Prime : do not underestimate.
Soma-and-Boltor-the-hoses-of-glory everyone already knows and loves (possibly too much).
Sniper/single-target nuking weapons:
Vectis : rapid-firing single-shot sniper, potentially highest single-target dps in the game with primed (and eventually primed charged) chamber.
Lanka : pure elemental charged sniper with punchthrough, potential for very high damage aoe procs.
Opticor : highest base-damage non-archwing weapon, long charge time mitigated by vile acceleration/shred. large AoE if aimed at a solid surface. lower dps than lanka or vectis.
Dread/Paris Prime : Highest damage per shot in the game coupled with knockback and punch-through, slower fire rate and poor longrange accuracy.
Sybaris : Halfway between latron prime and vectis, delivers very high and accurate burst damage at the expense of crowd control.
Heavy aoe/crowd control weapons:
Torid : Slap status chance and blast damage on this, and stuff just breakdances while DoT instances stack up.. Can also be stuck to allies, enemies and kubrows for additional hilarity.
Kohm : Now with more ammo efficiency! Repeatedly buffed (mistaken for nerfs by scrubs everywhere) to the point of absurdity, this is the first stop for handling huge waves of mobs in close quarters. Can be bounced off the floor for long-range shots.
Phage : Some of the highest sustained, unlimited-ammo dps and status in the game, limited onyl by close range. Able to use Viral+Corrosive as an added bonus.
Penta/Ogris : Was a thing, long, long ago.
Secondaries
Akmagnus : miniture, rapidfire latrons, capable of sniping or closerange hosing of 30-40k dps. only limited by long reload and small magazine.
Telos Akbolto : Miniture boltor prime, complete with half the clip size and significantly higher damage output. Telos edition comes with 5 more damage, more status and a powerful stacking gas AoE.
Synoid Gammacor : The noob-ray Mk2, ’nuffsaid.
Vaykor Marelok and Lex Prime : Good mid-range marksman pistols with very high damage/status, limited by reload, recoil and slow fire.
Acrid : Still godly. Every shot (regardless of status chance) deals additional poison damage equal to 50% of base damage (including all mods and bonuses from damage type) inflicted 9 (25 with augment mod) times over 8 (24) seconds. Truly outrageous.
Brakk : quack quack. Massively overrated but still very good.
Tysis : the last word in 100% status trolling. keep waves of mobs pinned to the floor for days.
Melee
Skana : 4 forma with prime reach, bright purity and crimson dervish. only for true masters.