What do you do whenever you are waiting for something in the public? Perhaps for departure in the airport, or for train or someone to arrive? Reading a story book is one of the options,but here I want to focus specifically on playing games.
The following is the ranked list of playable games/puzzles while waiting. I am a board game player, so I may be biased but I will give justification on why this or that is best, superior or inferior.
#5 : Mobile phone games
The problem with playing mobile phone games while waiting in the public is that your phone is exposed. This may make you a target for snatch thief. Besides, it consumes battery power, making playing to be limited. But of course the good thing is, you almost always have your mobile phone around. There is no need to bring extra materials.
To be fair, depending on the available software, mobile phone games can actually rank anywhere.
# 4 : Rubik’s cube
Rubik’s cube requires both hands to play, which can be problematic if you are standing in the train with one hand already occupied for balancing. Or in another example, one hand already occupied to hold documents when queueing for Visa application etc. Games that require both hands are not suitable in this case.
Since Rubik’s cube does not make you a snatch thief target, I rank it better than mobile phone games. Of course, another problem is, once you know how to solve it, it’s no longer mentally challenging to play.
On the good side, if you are a proud geek, playing Rubik’s cube in the public can be an excellent ego booster.You will have more chance to get awe from public especially kids compared to other games.
#3 and #2 : Crosswords and Sudoku
The main drawback of these two games is the same as previous, in that they require both hands. Moreover, holding a sharp object like pencil may not be a very good idea in crowded area due to risk of accidentally injuring others or self. I rank this better than Rubik’s cube because these games have many more levels of complexity and are more mentally challenging. 
You will also need to keep two objects for these games, pencil and the book. I find that annoying. But that is actually a good thing, as bringing along a pencil or pen everywhere is a good habit. Crossword game may be better than Sudoku, if you like to talk to strangers. Asking for help for certain parts of the game from person next to you can start a conversation and may earn you a great eternal friend. 
#1 : Tsumego
Tsumego is a life and death part of Go board game which asks the reader to visualise sequence to kill or save a group. It is quite similar to Chess problems i.e. Black to mate in 3.
Playing tsumego while waiting requires only one hand. All you need is to hold the book, look at the problems and visualise sequence. Answers usually available on the next page. Tsumego problems also have many levels of complexity, hence playable for all sorts of people. Playable with one hand and being an excellent and fun mental training game are some of the reasons of why I rank this first.
Well, that’s very quick opinion from me. I played all of the games before, but now I only do tsumego if I have to wait long for something. For those who do not know the rules of tsumego, just look up on the Internet and start learning. It’s very easy! You may start solving your first tsumego after few minutes.
So biased. I know. LOL
