Well I'm new here, but I joined to share a map I made (it's my first 'real' map so don't be too harsh) and I haven't seen any other maps like this (I'm sure there is but I haven't found one) so again, don't be too harsh.
This is a co-operative project between me and a friend (who doesn't have Halo sadly)
Here is the thread:http://www.bungie.net/Forums/posts.aspx?h3fileid=108209136
Features: A volcanic center piece (and in king of the hill games the hill)
On the volcano is 4 man canons to punish a wrong step by flinging you away.
4 Turrets to provide heavy fire.
2 bases with completely different layout.
Plenty of cover to protect infantry.
2 Mongooses and a Warthog in each base.
A Spartan laser on the volcano.
Blinding effect while on volcano to make staying on the hill difficult.

Long Version: This map is centered around a central volcano, which in King of the Hill games is the hill.
On the volcano is 4 man canons, these combined with the blinding effect of being too close to the volcano make it hard to both stay on the hill and maneuver effectively. The Spartan laser here is to prevent viechles reigning supreme.
The two team bases have diferent layouts ( I wont go into detail here since the screen shots would explain much better).
Both sides have 2 Mongooses (is that the right plural?) a warthog each and a variation of the sniper (beam rifle of sniper)
In between the bases and the volcano are lots of bits of cover to keep you safe from the four turrets surrounding the volcano.
The lack of grenades is on purpose, so one will not just waste their grenades knowing they will pick up some more two seconds later.
Like wise the lack of close range weapons is to encourage mid range combat and discourage camping in some rubble.

Birds eye view

Pre-Eruption

Blue Base

Blue Base Garage

Sniper Path

Red Base

Red Garage

Red Base Tunnel

Turrets
And Lastly a close up of the volcano.

Also I'm not entirely sure I've posted in the right place (please kindly say so if i haven't).