Trasher is the generic term for any card with the ability to trash one or more cards from your hand or deck. (Cards which trash another player's cards are considered trashing attacks, while cards that trash themselves are referred to as one-shots).
There are two main uses for trashers. The first is simply to eliminate weak cards from the deck ("deck-thinning"), in order to enable faster cycling and have more concentrated hands of useful cards—this chiefly involves trashing starting cards (Coppers and Estates or Shelters) and Curses, but can also apply to cards that were purchased for early-game use and have outlived their usefulness, such as cursers after the Curse pile is depleted.
The second is to receive some benefit from the act of trashing itself—either by trashing a card that has an on-trash effect, or because the trasher itself has a useful effect in addition to trashing. Trashers in this last category are often referred to under the umbrella term "trash for benefit", though sometimes (as below) the term specifically refers to trashers that give better benefits for trashing more powerful cards.
 Types of trashers
 Multi-card trashers
These cards allow rapid deck-thinning. Chapel is the multi-card trasher par excellence due to the combination of its cheap price and the large number of cards it lets you trash; other multi-card trashers usually offer benefits in addition to trashing, or alternative effects that keep the card relevant after you've trashed all the cards you want to trash.
- Dominion: Chapel, Sentry
- Intrigue: Steward, Trading Post
- Prosperity: Forge
- Mint has an on-buy trashing effect.
- Cornucopia: Remake
- Dark Ages: Mercenary, Count, Dame Anna
- Guilds: Doctor (which also has an on-buy trashing effect)
- Adventures: Amulet, Bonfire, Trade
- Empires: Temple, Donate
- Nocturne: Monastery, Bat
- Cemetery has an on-gain trashing effect
- Renaissance: Cathedral, Sewers (requires at least one other trasher)
- Promo: Sauna (dependent on how many Silvers you play)
 Trash for benefit
Several cards allow you to trash a card and receive a bonus or benefit that depends on the cost (or occasionally other properties) of the trashed card(s). These are commonly referred to as trash-for-benefit (or "TfB") cards (most trashers give you some benefit to your current turn other than trashing, and the term "trash-for-benefit" is sometimes used more broadly to refer to all such cards). Terminal TfB cards are usually soft terminals; when they collide with an expendable Action, they can use it for fodder, sometimes even to gain or buy a Province.
These are cards that allow you to trash one or more cards and gain cards to replace them depending on the cost of the trashed card. Some provide other benefits in addition to the gain. These cards usually improve your deck by trashing weaker cards for stronger cards, without substantially thinning your deck, because you gain in addition to trashing. Some remodelers, however, allow you to trash more cards than you gain (Forge), or require you to gain cards of a specific cost, allowing you to thin your deck if there are no available cards at that cost (Upgrade and Remake are the best examples of this). Some are restricted to trashing or gaining cards of specific types.
Many remodelers have names that are verbs.
- Dominion: Remodel, Mine
- Intrigue: Replace, Upgrade
- Prosperity: Expand, Forge
- Cornucopia: Remake
- Hinterlands: Develop
- Farmland has an on-buy remodeling effect.
- Dark Ages: Procession, Graverobber, Rebuild
- Guilds: Stonemason, Taxman, Butcher
- Adventures: Transmogrify
- Nocturne: Zombie Mason, Exorcist
- Renaissance: Improve
- Promo: Dismantle, Governor
Transmute, from Alchemy, gains a card depending on the type of the trashed card, rather than its cost. The Dark Ages cards Rats and Altar resemble remodelers in that they cause you to trash one card and gain another; but the card you trash has no effect on what card you might gain.
 Other trash-for-benefit cards
These cards provide benefits scaled to the cost of the trashed card, other than gaining cards whose cost depends on that of the trashed card:
- Seaside: Salvager
- Alchemy: Apprentice
- Prosperity: Bishop
- Hinterlands: Trader
- Adventures: Raze
- Empires: Ritual
- Renaissance: Research, Recruiter
 Borderline cases
- Dark Ages: Counterfeit provides a benefit scaled to the value of the trashed Treasure, rather than its cost.
- Empires: Catapult has an effect with a cost threshold, but not a scaling one.
- Empires: Sacrifice has an effect that depends on the trashed card's type, rather than its cost.
 Single-card trashers
These trashers have effects that are independent of the properties of the cards being trashed, and most can trash any card. These have a variety of uses: many are deck thinners or improvers; but for Death Cart, for example, which can only trash Action cards, the trashing is in part a penalty to compensate for the strong + effect.
- Intrigue: Lurker, Masquerade
- Seaside: Lookout
- Prosperity: Trade Route
- Dark Ages: Altar, Death Cart, Forager, Junk Dealer, Rats
- Altar and Rats resemble Remodelers in that they trash one card and gain one card, but what card can be gained is not dependent on what card is trashed.
- Adventures: Ratcatcher, Plan
- Empires: Small Castle, Advance
- Nocturne: The Flame's Gift, Goat, Zombie Apprentice
- Renaissance: Hideout, Priest
- Promo: Sauna in effect allows you to use Silver as a single-card trasher.
 Copper trashers
These cards are primarily used for trashing Copper: Moneylender and Ducat can only trash Copper, while the others can trash other Treasure cards as well, but do not provide better benefits for trashing more useful Treasures.
- Dominion: Moneylender
- Prosperity: Loan
- Mint's on-buy effect, while not a single-card trasher, is also best used for trashing Copper.
- Hinterlands: Spice Merchant
- Nocturne: Pooka
- Renaissance: Treasurer
- Ducat has an on-gain trashing effect
Trashing Copper is also an important function of Counterfeit and Catapult, though they do give more powerful effects for trashing more valuable (or expensive) Treasures. Miser removes Coppers from your deck without trashing them.
 Estate trashers
These cards can't trash Treasure cards and don't give better benefits for trashing better cards. Therefore in the early game they're most likely to be used for trashing Estates or Shelters specifically; later in the game, they may be used on Curses, obsolete early-game Actions, and cards with on-trash benefits.
These cards offer ways of removing cards from your deck other than trashing them. This can sometimes allow sneaky combos with Possession.
- Intrigue: Masquerade
- Masquerade both allows you to pseudo-trash a card by passing it away and allows you to actually trash another card.
- Seaside: Native Village, Ambassador, Island
- Adventures: Miser
- Promo: Prince
- (However, removing undesirable Action cards from the deck is not the best use of Prince.)