I had been lurking around for about 6 months now, but I felt this would be a good time to make a suggestion for a game: BattleForge. Given how excited Day[9] became at the deck building aspect of Hearthstone, I believe Sean would love this game. BattleForge is a joint Trading Card Game/RTS, which seems to combine the best of Starcraft 2 and games like Magic and Hearthstone. The basic idea is that you form a deck with varying strength cards, and those cards then become the available units for your custom "race." This lends a depth of strategy to deck building that a traditional card game could never compare to: do you fill your deck with tier 1 cards, the equivalent of zerglings, and hope to overrun your opponent early with cheese, or do you expand quickly to new bases, building orbs that allow you to use more powerful cards of higher "tiers"?

If you were to play this game, either on your own time or in your Day Off, I would suggest you read about it some beforehand. It has both a single player campaign (containing many co-op missions of varying size) and a ranked multiplayer ladder. New cards are gained either from a random lottery (not advised), or bought from other players in a fully functioning auction house, and it would be very advisable to have enough info on some types of units and decks to be able to make a smart deck. 

This is my Day Off suggestion. I hadn't seen any mention of it in the existing forums, and I think it is incredibly far up Sean's alley. If none of the other DayKnights(R) have heard of this game before, I highly suggest you all look it up as well. Very fun game by the makers of the Ultima series, I believe. Does something unique in genre of game, that becomes very fun to play.

- Vexon, of clan GRIMEY