I once built one called Night of the Living Deck that was fully populated with zombie cards. It built out a cheap creature army and then relied on getting a card that turned a target land into a Swamp. Zombies had swamp walk, so at that point the entire army could march past the defenders and just wipe the opponent.
I built it as a joke but it actually played pretty well and won a decent number of times. The best part was how angry people would get from losing to such a basic deck.
I loved my zombie deck with multiple Grave Titans and several destroy cards, but once an opponent figured out how it worked, the next deck they brought out would pretty much shut me down.
Oh yeah, if they know it’s coming it’s pretty easy to counter. The fun part is surprising them with a deck that’s so stupid but can still win. For me, it summed up the zombie genre.
My strongest deck design was a control/millstone deck that just carved through everybody until Necropotence came out, and I couldn’t beat the speed on that one.
I used to have a black card that just instantly destroyed all white creature cards in play; even your own. Their numbers didn't matter. Just their color. I called it my reverse race card.
They could play that and just checkmate you instantly.