かばん

How it works

This is an exclamation, not a full sentence. 鞄(かばん) (bag) is named first, then a pause, then a reaction to it. The adjective 重たい(おもたい) (heavy) is clipped to 重たっ(おもたっ) (so heavy!) — chopping off the ending and adding a small tense stop is a very casual, spoken way to blurt out a feeling the moment you notice it. No です (is) or は (topic), because you're just reacting out loud.