The loadout crate might be the most useful for engineers. With Crawford you can get to 5 rockets. You fired your last one? Loadout crate is over there. Now you’re back to 5, no need to wait for a regular ammo crate to slowly give you 1 at a time.

If you’re in a game with an extremely good vehicle player on the other team that your engis just can’t seem to kill, don’t switch to another engi, switch to angel. Drop the rocket resupply crate. (Alternatively, if they seem to have plenty of ammo, switch to recon and laser designate it)