For gondolas, there are so many possibilities.
Pipe, steel beams, steel coils (only if the car is specially equipped with coil troughs), steel plate, steel scrap, rail, ties, junk, telephone poles, steel wire in coils, logs, pulpwood.
Coal was often shipped in regular gondolas to small dealers that weren't set up to receive coal in hoppers. Labour was cheap back then, just hire a couple guys with shovels.
Most coal today is also shipped in unit trains of rotary dumping gondolas. Most people incorrectly identify these cars as hoppers though.
Woodchips are also carried in gondolas, but in special-purpose cars with tall sides because of the light weight of the load.
Gondolas can also be equipped with covers to protect their contents, usually when steel coils or quality steel plate and sheet is involved. Ore concentrates are also shipped in gondolas under cover, usually removeable fiberglass covers.
