Good to see another Al()ens fan on the boards.
I would love to see the Sulaco too. Or the dropship from Aliens for that matter.
I think to push some interest to the fantasy gamer aspect, whatever space vehicle is made should be a form of fantasy craft instead of your usual shuttle, just so do two birds with one stone i guess.
For air i think a Jet fighter with afterburner option could show more from the engine in terms of speed and jet handling (if its there to show in that way anyway) maybe an F-15?
for roads i agree a sports car, just6 to give some flash, im not sure on copyright issues but id say a Bugati Veyron again to just appeal to some crowds out there.
These are choices i think best for the promotion of the engine, my personal choices are a Dodge Ram pickup, a Eurofighter as the Jet, and for space something designed by the team themselves that could be launched from land in a sort of near future level of technology but different from your usual shuttle, a bit like the Delta Glider i guess.