stop sayin grunt110 cant count, if you read his post you will notice there are two ideas two in #3.
ok, grunt110 i will be nice and step you through to the modding world, hope these tuts help.
Before i say anything, do anything, type anything or anything, i will stress to you to
BACKUP YOUR MAPS!.
heres how:
make a new folder on your desktop, and go to your maps directory and push, ctrl+a(or right click and select 'select all') then ctrl+c(or right click and select 'copy') then go to your folder on your desktop and paste them all in there by pushing wither ctrl+v or right clicking and clicking 'paste'.
wait the long ass time it takes, and
then start these tutorials, and dont be cheap, like me or else you will have to pay the price,
Reinstall Halo! 
(like i had to

)
ok go on...
You will need:
halo map tools
thats all.
Idea number 1
grunt110 wrote:1. i think some one should make a mod where plasma weapons dont over charge
O.K open hmt3 and click file>open and go to your maps directory and select the map you want, for now, we will select 'bloodgulch.map'.
now go to the tag that says '[weap]Weapon(20 items)' and double click it or click the plus next to it. then scroll down to a plasma weapon, say, the plasma rifle 'weapons\plasma rifle\plasma rifle' and click it. it will bring up a heap of info on the right, click the menu next to 'Projectile' and select 0, then go down to 'overload time' and it says 0,wait , thats wierd. sorry, cant help you with this idea....
Idea number 2
grunt110 wrote:2. how about a sniper rifle hat shoots as fast as an asault rifle and has the same amount of ammo in the clip if its possible
now this one i know is possible, repeat the steps to open your map file and go to '[weap]Weapon(20 items)' again and click 'weapon\sniper rifle\sniper rifle' the info on the right will appear again, yet again, click the menu next to 'projectile' and select 0. then go down to 'minimum ROF' and enter 15 where it says 2, do the same for 'maximum ROF'. there you go, you have now changed the sniper rifle ROF.
Idea number 3
grunt110 wrote:3. these two ae probably unlikely to work but ill say them anyway. how about a worthog that has the oppisite of the gun in back in the passenger seat(i.e. a rocket launcher in the back and a chain gun in the front and vise versa) And a ghost the holds more than one person
Im sorry, i dont know how to do this one yet, ill probably make a thread when its done, altho i might have a problem positiong the 2nd person...
Idea number 4
grunt110 wrote:4. a fun mod would be if the banshees primary plasma gun shoots rockets instead and if u can a nuke for the secondary gun( i saw the nuke projectile on bg and thought itd be cool in a banshee)
i can do the rocket part, unfortunately i dunno how to make nuke, but anyway, here:
k reapeat procedure until you have opened up bloodgulch, now open up '[proj]Projectile(21 items)' and go down to 'vehicle\banshee\banshee bolt' and click it, now, up the top more there should be a box labled 'Tag Information' and just below that there should be something looking like this,

click 'swap' and double click the second one '(B3E630)vehicles\scorpion\tank shell' now click 'save' and go and play it!
so thats it from me, plz dont disregard this tutorial, it took me a long time.