What monster/trap would make a good sentry turret?

[Colmarr]

For an upcoming encounter in my Zeitgeist campaign, I want to surprise my players with a steampunk equivalent of the sentry guns from Aliens:

[ame="http://www.youtube.com/watch?v=HQDy-5IQvuU"]sentry turrets from Aliens[/ame].​

Obviously a fully automatic turret is inappropriate for a fantasy campaign (even a steampunk one), but I'm looking for something with a similar flavour - an advanced weaponry system capable of self-targeting and multiple attacks.

So, what 4e monsters or traps would you reskin to make such a thing (and where can that creature or monster be found? I have lots of books but no access to the compendium)?

 

[The Human Target]

Magic Crossbow Turret Dungeon 183
Elite Magic Crossbow Turret Dungeon 157
Dwarven Crossbow Turret Orcs of Stonefang Pass
Crossbow Turret Thunderspire Labyrinth
Ballista Platform Dungeon 168

 

[(Psi)SeveredHead]

Any of those might work; I'd try to have each turret have an AoE option.

What are they firing (magic? physical?) and how fast? If fast enough, it could turn into pinning fire. (In that case, reduce damage by 1/4, targets take penalties to hit and can choose to drop prone or take the damage.)

 

[Colmarr]

Dwarven Crossbow Turret Orcs of Stonefang Pass

Just what I was looking for. Thanks

 

[The Human Target]

No problem!

I enjoy the occasional times when I'm useful.