Trashing Estates in Dominion
Multi-card trashing, when available, is usually the best way to open the game. Indeed, as The Chaz says, you want to get rid of your coppers as well your estates. 

Theory's writeup on the chapel gives a thorough coverage of the quality of dense decks.  You can also see how many of the best openings from the 6 million games played online involve the chapel.

Trashing with single card trashers like Remodel and Develop are less pressing and often not the best opening.