Arkham Noir is a fun solo card game set in the Lovecraft Universe. You can find a print and play for Case 2: The King In Yellow at the link (no need to have played Case 1 — they are standalone games).
Warflag has some modifications for the commercial Age of Reason rules to allow you tu use them to fight battles in the Age of Marlborough.
By the Rule is a free print and play card game with just 18 cards. The author describes it as “A quick little game of playing by the rules … but only for liars and cheats!”
Pocket Civilization is a free, downloadable solo civilization building game that’s advertised as being compact enough to play on an airplane.
It looks very cool, and the Board Game Geek reviews are favorable.
Days of Wonder’s Battlelore has lots of fiddly bits that need organizing. The BattleBox project offers pdf downloads for a series of foldable storage boxes.