A boring encounter can get exciting in a hurry through the skillful application of Alchemist's Fire. I think it's one of the most underrated weapons in the game.
Sure, the target takes 1d4 fire damage. No big deal, right? Well, the target also catches fire, automatically taking 1d4 damage each round until it spends its action to put itself out with a DC 10 ability check. Also not that big of a deal, you're probably thinking. But look closer: there's no save against the ongoing damage, and preventing that damage will cost the target its action. That's rare.
And that damage is cumulative, too. Hit with 2 vials of alchemist fire? That 2d4 fire damage/round, no save, and 2 actions required to put the fire out. Hit with 6 vials? 6d4 fire damage/round, no save, 6 actions required to put the fire out. If your whole crew lobs a volley of alchemist's fire in Round 1, your target will be in a world of hurt come Round 4.