I have something against puzzles like this, because they aren't provided along with the information needed to solve them. Has the king or the rook moved or not? Still, nice one!
Hardest tactic ever!!!!!

Hey guys here's a tactic very few people can solve
More like..."very few people who have never played chess"

Csstling and en passant puzzles are sneaky but common enough that it's easy for many of us to anticipate.

Nice exercise. This can come up in regular games too and another idea on this is if you have swapped Queens and then castle long if the opponent takes with his KIng. It places him in check and also protects your King. You can see this in many games where Black plays the Philidor.
Hey guys here's a tactic very few people can solve
White to play checkmate in 1
here's a nice quote
"Strategy without tactics is the slowest route to defeat.
Tactics before strategy is the noise before defeat"
-Sun Tzu