I think Watchtower deserves a special mention in this article. Not only is the reaction ability useful in your buy phase when the card isn't played, but if you're trying to get good Watchtower coverage for defense against a curser, I've found it's better to not play the Watchtowers more often than it is to play them. This, coupled with careful deck tracking (both you and your opponent) turns Watchtower-based defense from a luck-fest into an actual solid strategy.
$3 and a Watchtower in hand? Top-deck a WT for next turn! Knowing if your opponent has seen their curser this shuffle yet, or how many WTs are left in your draw/discard, or where you are in your shuffle are also factors that weigh into this.
...and I wouldn't have even thought of this if it weren't for WW's commentary on his videos. So many tactical insights there that have really improved my game.