Make a model and bitmaps of sandbags.

Make it so that the trails of the bullets of the sniper rifle don't show; so they don't give off your position.
Make a model and bitmaps of an artillery.

Make a model and bitmaps of an armored train.

Make a model and suitable bitmaps for an improvement of the scorpion tank.
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Make a model and suitable bitmaps for an improvement of the shotgun.
Make a model and suitable bitmaps for an improvement of the pistol.

Make a model and bitmaps for a buggy.

Make a model and bitmaps of a humvee hardtop.

Make a model and bitmaps of british motorcycles.

Make a model and suitable bitmaps for an imrovement of the sniper rifle.

Make a model and bitmaps of a helicopter. (One seat can be driver and the other can be gunner.)
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Make a model and bitmaps of a Panzerschrek.

Make a cooler skin for the plasma rifle.
Make a civilian warthog with a tire on the back of it. (Make sure to make it fast.)
If you'd like to help me with any of these, then you'll be welcome to, i'll be sure to give you all credit. You can do as much as you want as long as you can do them. These will be great mods for Halo PC!