What they wore*:

  according to the autopsies

Dylan -- Black cargo pants, a black T-shirt that said Wrath in red across the front, black baseball cap (worn backwards), and a black trenchcoat (leather duster, really). Also wore a black fingerless glove on his left hand and black combat boots. Had a red medallion on his left boot bearing a sickle and hammer. Black suspenders were found close to his body.

Eric -- Black fatigue-style pants, a white T-shirt inscribed with the words Natural Selection on the front, black baseball cap with the letters "KMFDM" on it (worn backwards), and a black trenchcoat (duster). Wore a black fingerless glove on his right hand and black combat boots.

Both wore utility belts which held pouches filled with shotgun shells and they carried CO2 bombs and clips of 9 mm bullets in their pants. Also, both had match strikers taped to their forearms, presumably to be used to easily light their bombs.

 

Shots Fired**:
** according to CNN's coverage of the Columbine Report

Dylan --
9mm rounds fired:
outside the school: 3, inside the school: 31, library: 21
(total 55)
Shotgun rounds fired:
outside the school: 2, inside the school: 4, library: 6
(total 12)
Total rounds fired: 67

Eric --
9mm rounds fired:
outside the school: 47, inside the school: 36, library: 13
(total 96)
Shotgun rounds fired:
inside the school: 4, Library: 21
(total 25)
Total rounds fired: 121


Bomb Tally:
48 -- Carbon Dioxide bombs
27 -- Pipe bombs
11 -- 1.5 gallon propane bombs
  7 -- gas or napalm bombs
  2 -- 20 pound propane bombs


Info from CNN:

Only two shots can be fired from a double-barreled shotgun before the shooter must reload by breaking the barrel open, manually inserting two new rounds, and closing the gun. A pump shotgun can be fired as fast as the gunman can pump and shoot. It shoots much faster than the double-barreled type because spent shells are ejected and a live shell manually slides into place. A gunman can shoot five rounds with the pump shotgun before the weapon must be reloaded.

 

What they carried**:

** according to CNN's coverage of the Columbine Report Dylan -- Intratec TEC DC-9 (9-mm semi-automatic handgun) attached to a strap slung over his shoulder (under coat), Savage 311-D 12-gauge double-barrel shotgun (barrel sawed down to approximately 23 inches, initially half-hidden in Dylan's cargos).

Eric -- 10-shot Hi-Point model 995 carbine rifle on a strap (under coat), Savage-Springfield 67H 12-gauge pump shotgun he called 'Arlene' (named after a Doom character - initially in one of the duffels carried to the top of the grassy knoll -- stock and barrel sawed off, reducing the entire gun to 26 inches).

The sawed-off weapons, both around 30 years old, were so short that firing repeatedly from them caused their hands to bleed on the practice range initially. They apparently acclimatized to the weapons over the months preceding the shootings. Both gunmen also carried several knives, but they did not use them on April 20. They named their pipe bombs. Four bombs are mentioned on Eric's website, along with their specs. 'Vengeance'  and 'Atlanta' were found at the Klebold residence when police searched it.