I use it a lot for things like Stunning an engineer who is hammering on a turret, usually while we have an uber going to take it out.
Firing it into groups of people during a big firefight and helping my team by stunning one of the players in the fight Smacking heavies who are shooting with it, then running up on them and popping shots into them.
Stunning anyone guarding a flag that I want to pick up There are more uses than that
but, that is my main usage of it.
I've found it pretty useful in certain circumstances.
gaming.stackexchange.com/users/44/Corv1nus
When fighting alone, the Sandman is a wash at best, because the small window of opportunity you get from the stun is offset by your reduced survival rate due to the health drop.
The Sandman is much more effective when used as part of a team push, or even only sniper cover, as stunned foes make excellent targets for Rockets, Grenades, or Headshots.
Target also matters --
If there's an enemy heavy parked on a control point, he makes a much better target (both in terms of ease of hitting and in terms of net effect) than a scout or spy.
If you primarily play the scout as a harasser, you may also find more use for the sandman, because getting stunned is, if nothing else, quite annoying to the recipient.
gaming.stackexchange.com/users/336/Raven Dreamer
It's somewhat useful on melee-only maps, since the bat counts as melee, but you still get a ranged attack out of it.
gaming.stackexchange.com/users/3319/Allen Gould
Recent patches have added the Flying Guillotine, a ranged secondary that deals damage based on distance thrown.
The biggest pro of it is that it will deal critical hits (150 base damage including crits) on stunned players.
I've found it extremely useful in taking down Heavies.
First you stun them, then lob a guillotine into them.
That's 150 damage instantaneous damage, not to mention the bleed damage the guillotine causes.
A couple scatter shots into them, and you're good to go.
Essentially, paring the Sandman with the Guillotine is a devastating combo on unexpecting players.
Here's a video of it in action.
http://wiki.teamfortress.com/wiki/Flying_Guillotine
gaming.stackexchange.com/users/18916/korrasaur
Another useful situation is if there is a single opponent pushing the cart in a payload or payload race map.
gaming.stackexchange.com/users/306/Albort
I recently unlocked the Sandman for the Scout and have been using it but I don't really see the advantages.  The -15 health does not seem to make up for the fact that I am just able to stun a player for just a few seconds.  Is the Sandman only used to make a quick get-away or is it used effectively in combat?
What is an effective way to use the Sandman?
gaming.stackexchange.com
<team-fortress-2><tf2-scout>
gaming.stackexchange.com/questions/3376
gaming.stackexchange.com/users/346/cruzja
You can use it for stunning and engineer or on melee only maps. There are a variety of opinions around about this, some say its useful for stunning an engineer for example, others say it can be sometimes handy on melee only maps. Some people also actively avoid it since it does not provide any good advantages.
User uses it for a variety of things. User find it quite useful in certain situations, like on melee only maps. User does not find it particularly useful.