I realize that the qualifications are sort of restrictive, but I’m looking for games you can play with yourself while doing basically anything; walking, sitting on the train, etc. If they exist, anyway. The scope can be liberally interpreted to include games that require only pencil and paper, for those times we’re trapped at tables and such.
(Mods, if this is in the wrong forum, feel free to move it.)
One of mine is: Try to find something in your immediate environment for every letter in the alphabet (i.e. in your living room: atlas, bookcase, chair, door, eraser…).
If you have a pen or pencil, try seeing how many things you can do with it while keeping it airborne (i.e. rolling it off the back of your hand, using your head or shoulders or biceps, etc.). More for when you’re alone in a room 
If there are a lot of people around, see how long you can track someone walking. Try to figure out where they’re going. Try to figure out their life history. Try to figure out how much their clothes cost.
Eavesdrop and try to memorize as much of the conversation as possible (sorry, if you’re in public talking in line or in a restaurant at a normal volume, your words are for the world to hear). Later, record the conversation. I did this a few times when I was taking a fiction writing class, and twas actually quite fun…
I like this play-anywhere solitaire card game. I learned it as “Accordion”, but it doesn’t exactly match any of the games of that name I’m finding online. It’s an idoit’s game (you don’t have any choices) but I find it strangely soothing. And you don’t need any room to play it, just a deck of cards, two free hands, and somewhere to drop discards (like your lap.)
Hold the deck, face down, in your left hand. Pull the bottom card of the deck, and place it face up on top of the deck. Pull the second card in the same manner, and place it on top, but offset a little bit so you can see both cards. Continue pulling cards in this way, holding the cards so that the top four are visible. If at any point the first and fourth cards are the same suit, discard the two cards between them (the second and third.) If at any point the first and fourth cards are the same value, discard all four top cards.
When you’ve run out of facedown cards in the deck, the game is over.
The winning conditions are fairly nebulous, but I feel that a game where you’re left with four or fewer cards is pretty good.
Podkayne, I can’t believe I’ve finally found someone else who knows that game! I’ve played it ever since I was a little girl, and have never seen it anywhere else. I don’t know who taught me (my mom?), and we never did have a name for it, but it is just a simple, no-thinking fun little game.
This is a good one that can be done with just a deck of cards, no need for anywhere to lay them down, just holding the cards in your hands.
Shuffle the cards first. Then… name a rank of card (seven, queen, etcetera,) and flip up the top card of the deck. If it’s of that rank, you lose, otherwise you can put that card face up at the bottom of the deck (so it’s completely obvious once you’ve gone through the whole thing,) and try again. If you can get through the deck without losing, obviously you win.
I can’t remember offhand what the name of the game is. Starts off being pure luck, of course, but then there’s a little opportunity for skill, because the more cards of a given rank have been turned up, the less likely they it is to be the next card turned up. On the other hand, especially if the deck hasn’t been shuffled too thoroughly, there’s a weird tendency for cards of the same rank to appear near each other, so you don’t necessarily want to call exactly the same rank that has just appeared.
And, once you’ve noticed that all four nines, say, have already come through, then you’re home free and can just finish off the pack on that rank, ‘nine.’
When I was bored I used to write down all 50 states from memory as a challenge.
It’s gotten to easy now though.
You can do this with anything, though.
Challenge yourself to learn all the provinces in Canada. Practice them.
Into D&D? Recite one mythical creature for each letter of the alphabet. For bonus points, recite an ability they have.
How about cars? Come up with a car name for each letter, then for bonus points - manufacturer.
chrisk, the version I play is that you start by naming the Ace, then flip the top card. If it matches, you lose. If it doesn’t, keep going. Next card, Two. Next, Three. and so on. When you get to the King, the next card is Ace again.
Seems like it’d be easy to win, but it maybe happens 5% of the time.
diecast cars, glad to hear I’m not crazy! I wasn’t sure how well I was remembering the rules. I learned the game from a friend in college.
Knowed Out, I think if the cards are randomly distributed, you have a 12 in 13 chance of “surviving” each draw, but you have to survive it 52 times, so the odds of winning are (12/13)^52, or 1.6%.
I’m not accounting for certain numbers getting weeded out, so the odds might be better than that, but I can’t think of how to incorporate that.
Or just pick a category (eg. rock bands, birds, cities, cartoon characters, etc.) and try to come up with one example from that category for each letter of the alphabet. Alternative: for each one you think of, the next one has to start with the last letter of the previous example. This can be played solitaire or by more than one person.
Old stand-by pencil-and-paper games: Pick a long word, then see how many other words you can make using only the letters in the long word.
Pick two shortish words of the same length, and try to get from one to the other by changing only one letter at a time, each time making a real English word. (This one was invented by Lewis Carroll, by the way). Example: change HEAT to COLD:
HEAT
BEAT
BOAT
COAT
COLT
COLD
As for games you can play with yourself, there’s always MASTURBATING LIKE A MOTHER FUCK.
Or recite poetry from memory. One of the pieces I do is usually ‘La Belle Dame Sans Merci’ by Keats. Unfortunately, it’s frustrating when I can’t remember how it goes.