Demoman has two weapon modes for his grenade launcher:
The standard mode fires off grenades that bounce and explode after a couple of seconds.
In this mode try and use the terrain to your advantage, bounce grenades off walls to get them down corridors/alleys.
Another nice trick is to fire them high so they drop down, this takes some skill to time right and works a treat against players who look down a lot as they don’t notice the grenade till it’s too late.
If you are on the run with an enemy on your arse run through a doorway but leave a surprise behind by firing a grenade just above the door before you go through. The grenade should bounce back down the hall and with luck, land right in the lap of the oncoming aggressor just prior to unloading it’s neatly gift wrapped boom!
The other mode fires up to 8 sticky bombs in a mag. These are great for ambushes or protecting targets.
The trick here is to remember that you can have up to 8 stickies out at any one time and remember that you can detonate using the right mouse key. Detonation works in either mode.
One tactic is to protect engineers on your team by popping some stickies around his dispenser and gun turret, as soon as a spy tries to damage the turret detonate… easy kill. If Friendly fire is off this works great as you don’t damage your own team.
Remember always to switch back to standard mode when you’ve offloaded a set of stickies so you aren’t left defenseless, right click in either gun mode detonates the stickies you left.
You can, if you think quick enough use the sticky mode like a shotgun. The trick is to fire a sticky and detonate just as it reaches the target, inexperienced players might know they are sticky bombs but hopefully will be all too unaware of your ability to unload the Boom! just at the right moment :0)