Spears
Man, ain't no-one gonna endure getting the pointy end of a stick jabbed at them without some decent reflexes!
Spears skill determines your effectiveness while using polearms. Spears are generally much heavier than standard weapons, and are usually quite slow, but have high damage output to offput it. Spears most commonly do stabbing damage, though some do Slash as well.
Advantages
High-end spears such as the Chainsaw lance, Garden Weasel or Zap Brannigan tend to be very damaging and scale very well with brawn and endurance. They also can accept a wide range of mods compared to other weapons. Every spear is also at least PC1, and still more are PC2, allowing you to parry fists and whips with ease.
Disadvantages
Spears are very heavy, compared to other weapons. They're also generally very slow and take a lot of reflexes to reach usual speed, and are still beaten out easily by Whips and Fists.
Weapons
Sharpened Chopstick - Able to be improvised. Very weak, only really used for grinding.
Sharp Pole - Another grind weapon, slightly better than the military fork for damage. Can be bought in Ammu-Nation
Military Fork - Can grind up to 3 raw, lower minimum damage than the Sharp Pole. Can be bought in Ammu-Nation
Infected Syringe - Effectively a one-shot weapon, infects anyone who it hits without Hyperimmune with Ebola and causes large amounts of bleeding. Sometimes used by serial killers and drops off of Doctor Shunt.
Signpost Spear - Sometimes drops off of crackheads, slightly better damage than Military Fork and Sharp Pole. Rarely sold by Ammu-Nation.
Spike Spear - Very slow. Occasionally drops off of racists and J'Mak, not typically sold by Ammu-Nation.
Assegai - Very good scaling and damage, able to be found in stormfront and necropolis.
Luftspeer - Premodded with balanced grip, monowire and sharpening kit.
Large Scythe - Dropped by Nuns, but quite slow. Excellent damage.
Rusty Scythe - Easily acquired from the farmhouse west of Freedom City, past the chemical plant, and does excellent damage, but is very, very, VERY slow.
Pitchfork - Same as the rusty scythe, except with stab damage instead of slash. Dropped by farmers in Maco.
Corrosive Pike - Does rare corrosive damage. A spear so average, it's okay! Only acquired by craft.
Abossegai - Same as an assegai, premodded with Monowire Serrator, Sharpening kit and Balanced Grip.
Garden Weasel - Very good spear all around, with good speed and damage, formerly the best spear in the game.
Les Paul Drilltar - It's a fucking drill. On a guitar. Gift from admins only.
Chainsaw Lance - Excellent weapon for brawny builds, scales excellent with brawn, but a little slow. Can be gotten from Hawthorn or crafted on the Blacksmith forge.
Titanium Bo Staff - One of the new spears top-tier spears, extremely powerful and fast at doling out beat damage. Crafted.
Zap Brannigan - The best spear in the game, on par with the chainsaw lance. Does boatloads of shock and stab damage while turned on, and mediocre while turned off. Requires power adapters. Craft only.
Mods
Elemental - Either butane or shock mods. Only put EMP on specialized weapons to use for ghostbusting.
Grip - Always use balanced grip, to counteract slow speed on the majority of spears.
Monowire Serrator - Best used on the Chainsaw Lance, although it works just as well on everything else for brawn builds.
Strategy
PVE Garden Weasel or dual-wielded assegais can very easily cut down most mobs, use power attacks liberally.
PVP PC2 on the vast majority of spears is a definite bonus in PvP, and the chainsaw lance can cut through most soaks by value of bleed damage.