If the models are blacklisted or you can't use creator, just use Adv dupe. But to get around the blacklist you have to either edit the dupe so it has a different model, or just use model manipulator on it. You can only edit Adv dupe 1 dupes, though.
If a server has precision tool or no collide with world, you can get anywhere. Including skybox etc. It's alot easier to just use Hoverdrive Controllers, though.
Airboats go through walls if they're spawned inside them.
Also, some servers have the car dealer job or make you have to buy vehicles. But sometimes they don't let you tool/physgun them.
I'm not sure where to post this exactly, so I'll just leave it here.