Goblets are a type of container for drinks. They are similar to modern cups or mugs, but often more have the shape of a long stem like a wine glass, but with a more bowl like container.
Goblets are a common item to find in many houses made out of cheap metal or wood and aren't valued with a high price. They are often used as a background item which can sometimes be picked up and thrown as a distraction tool, sometimes cannot. At least one can be found in most T1/TG and T2 missions.
These are not to be confused with the more pricey Goblets which can be found in all three games as Loot items.