Demoman is the shortened (and perhaps more common) name for the demolitions man class in Team Fortress Classic for Half-Life. It is comparable to the Quake Team Fortress demolitions man.

The demoman has a medium amount of health and armor, as well as average speed. However, his weapons are definitely not average.

The grenade launcher propels explosive grenades in an arc toward their target. These grenades will bounce off walls (which is useful for firing around corners) and will explode after a couple seconds or when they hit a player. The grenade launcher holds 6 grenades or pipebombs (they are interchangeable). It is reloaded in shotgun fashion, by which I mean that firing can commence after any number of grenades are loaded into it. The grenades do significant damage to any target they hit and the explosions tend to bounce people around and disorient them.

The pipebomb launcher acts in a similar manner, except that the grenades are green instead of blue and they don’t explode for a couple of minutes. The player can trigger them at any time before then by hitting his special or alternate fire key (usually the right mouse button). This is useful for setting up traps around an objective or in a tight passage. A demoman can only lay 8 pipebombs at one time, after that firing any more causes the oldest pipebomb to explode. Another use is the pipe-jump, which involves triggering the pipes just as you jump over them to launch yourself across the map. This sort of activity will cause severe injuries, so it is best left to classes with concussion grenades. If the jump is properly timed, a demoman can survive a 4 pipebomb blast, but in combat you should never use more than 2 or 3.

The single-barrel shotgun is the demoman’s “long range” weapon (that’s sarcasm folks). It does have a longer range than the super shotgun, but does significantly less damage. Pull this weapon out after you’ve expended your 6 pipebombs to finish off those tougher opponents. It’s also useful when making a run through sniper-infested courtyards.

The crowbar is the standard last resort weapon. Get close and whack ‘em.

The demoman can carry 4 standard fragmentation grenades and 2 MIRV grenades. MIRV grenades explode spreading several smaller grenades around the area. These explode after a few more seconds. This is the deadliest grenade in the game.

One of the demoman's most useful items is the detpack. As a weapon, the detpack does more damage than any other. As a tool, the detpack can give a team a crucial advantage. To plant a detpack the demoman must hold down his +det5, +det20, or +det50 button for a little over 3 seconds. During this time he is defensless, but he can stop setting it at any time by letting go of the button. After it is set he will have either 5, 20, or 50 seconds (depending on which button he used) to flee the area before it explodes. The explosion will take out anyone within about a 15-yard radius (it’s kinda hard to judge this), but it will not go through walls. It will also trigger certain effects in the map (like destroying a wall or grate).

These weapons make the demoman the optimum high explosive delivery vehicle. With the MIRV grenades and bouncing pipes he can take down any defenses with extreme prejudice; he can launch himself to any area of the map by pipe-jumping and rain destruction down on his hapless foes; and, he can set up an impenetrable wall of pure explosive power on defense. The demoman is truly a fearsome opponent.

Some useful binds (hit ~ to get to your console):
special – detonates any pipebombs laying around
+attack2 – same as special (one of these is usually already bound)
+det5 – set a detpack for 5 seconds
+det20 – set a detpack for 20 seconds
+det50 – set a detpack for 50 seconds
detstart x – set a detpack for x seconds (you wont be able to stop in the middle of setting this)

Demolitions Man

Max Health: 90
Max Armor: 120 Medium Armor
Max Speed: Medium

Grenade + Pipebomb Launcher,
Single-Barrel Shotgun, Crowbar

Hand Grenades, MIRV Grenades

Can set large explosive devices.

(Taken from TFC in-game info.)