Flip Doom Donuts after activating Zero Force to clear all monsters with zero attack or defense off the field. Useful when with the above monsters that won't be affected by Zero Force, allowing them to attack directly.
No card is "trash." When used properly, they can be very good, its just that people overuse certain decks to the point where most other cards are inviable competitively (resulting in the use of staples). Casually though? It's alright.