Vehicles
Here are a couple vehicles I'll be using. Because I'm lazy, I just adapted what I found in D20 Modern and D20 Future. All these things will have different names in the campaign.
[I based this one on the civilian Hummer in D20 Modern. It's not quite the rockin' dune buggy the Halo Warthog is.]
Warthog
Has resilium armor (+6/-2) and twin thunder machine gun. Gives passengers ¾ cover.
Crew: 1; Passengers: 3; Cargo: 1,000 lb.; Init: -1; Maneuver: -3; Top Speed: 140 (14); Defense: 14; Hardness: 7; Hit Points: 38; Size: H.
[Ok, this isn't in Halo, but it's gonna be in my campaign.]
EU2A1 Mendez (APC)
Has resilium armor and 2 twin thunder machine guns. Gives passengers full cover.
Crew: 3; Passengers: 8; Cargo: M; Init: -1; Maneuver: -3; Top Speed: 95 (9); Defense: 12; Hardness: 15; Hit Points: 56; Size: G.
[Kind of a glom of the hover bike and hover car in D20 Future. I thought one plasma cannon and one fuel rod cannon was enough.]
Banshee
Has reactive armor (+8/-2), plasma cannon and a fuel rod cannon. Gives passenger ¾ cover.
Crew: 1; Passengers: 0; Cargo: D; Init: +1; Maneuver: +0; Top Speed: 245 (24); Defense: 16; Hardness: 5; Hit Points: 25; Size: L.
[Oh yeah, you might want the heavy weapon stats too. The twin thunder comes right out of D20 Future. Did you know that, according to the vague rules in that book, the twin thunder does not require Exotic Firearms Proficiency?]
Plasma Cannon
Damage: 2d12; Damage Type: Plasma; Range Increment: 100 ft.; Rate of Fire: A; Magazine: unlimited; Size: Huge; Weight: N/A (always mounted on vehicle).
[I've changed all plasma weapons' damage type from Fire to Plasma. Objects take only half damage from energy attacks--we can't have that. Plasma attacks deal full damage to objects and extra damage to energy shields (per rules mentioned in an earlier post).]
[Anyone think the fuel rod cannon should do more damage? What about it's weight?]
Fuel Rod Cannon
Works like a grenade launcher. Has poor heat sink gadget. Explodes in a 15 ft. radius (Reflex DC 15).
Damage: 4d6; Critical: -; Damage Type: Plasma; Range Increment: 70 ft.; Rate of Fire: S; Magazine: 4 box; Size: Huge; Weight: X.
More to come: Tanks, drop ships, Ghost. Maybe I can figure out a way to stick in the D20 Future hoverboard...