Here's a few things I brainstormed, most of which doesn't have a decent name or description yet, and balance is probably a bit off too. I glanced through this thread but I don't remember everything, so there might be some similarities to other stuff.
Three melee exotics:
Sledgehammer, or Maul, or what have you
Exotic Weapon
Inventory description: A very heavy metal hammer. Put your back into it!
Damage: 4d6
Damage Type: Physical
Accuracy: +0
Clip: n/a
FireSpeed: 1.0s
ReloadSpeed: n/a
Special: Has knockback comparable to a point-blank double shotgun blast.
Not necessarily your primary weapon, but could be useful for knocking baddies into lava or getting some breathing room when somebody gets up in your face, maybe juggle a rocket launcher out afterwards.
Shiv
Exotic Weapon
Inventory description: A small knife, ideal for holding in one hand.
Damage: 2d4
Damage Type: Physical
Accuracy: +0
Clip: n/a
FireSpeed: 1.0s
ReloadSpeed: n/a
Special: Stick it in your prepared slot and you get a free attack with it every time you attack an enemy in melee range, even if you use a ranged weapon. This attack occurs before your primary weapon's. If in your weapon slot or you attack without a melee weapon, you take a swing with you fist and the Shiv.
For a non-meleer, it can help buy a little breathing room when monsters get in your face. With a melee build, it helps you tear through enemies even faster and increases the chance of berserking with time, at the cost of reducing the chance of berserking per enemy.
Quick Knife (seriously terrible name)
Exotic Weapon
Inventory description: A knife so finely balanced you could probably fillet a charing dinosaur with it.
Damage: 2d5
Damage Type: Physical
Accuracy: +0
Clip: n/a
FireSpeed: 0.5s
ReloadSpeed: n/a
Special: none
It just hits fast, making Brute and SoB add up fast. One level of Brute takes it above the Chainsaw against unarmored opponents, and it's good for cutting through packs of weaklings without being as potent as Blademaster.
Other stuff:
Bolide
Unique Weapon
Inventory description: Less explosive than regular rockets, but just as deadly.
Damage: 5d5, radius 1
Damage Type: Fire
Accuracy: +5
Clip: 2 rocket (uses 2 per shot)
FireSpeed: 1.0s
ReloadSpeed: 2.5s
Special: No knockback. Fills the blast area with lava.
A safer, portable, miniature napalm barrel. Create moats, destroy corpses, or lay the hurt on trapped enemies. Completely useless against cacodemons and such, plus it's an ammo hog and dangerous to reload under pressure.
Ablative Armor
Unique Armor
Inventory description: Designed to shed its outer layers rather than melt, keeping you cool even in a plasma storm.
Protection: 3
Durability: 100%
Move Speed: -20%
Knockback: +0%
Special: Treats fire damage as shrapnel damage. Treats plasma damage as physical damage.
Mirage Armor
Unique Armor
Inventory description: If you didn't know where you were, you'd swear you were over there.
Protection: 2
Durability: 100%
Move Speed: +0%
Knockback: +0%
Special: Monster projectiles get -2 to-hit against you, no penalty against other monsters. Arch-vile and Revenant attacks have a good chance (20%?) of targeting an adjacent square; when "You dodge!" the attack can't center on your current square, either.
Devil's Eye
Unique Item
Inventory description: A gooey eyeball you found on the ground. It appears to ogle disconcertingly when you squeeze it.
Special: It's 'u'sed from your inventory like the Hell Staff, and tires you out. It shoots out a cone spread like a double shotgun, and all in its path lose 1/3 of current health, capped at 20.