Finding a good book while browsing at a book store. I still do it the old-fashioned way, and may continue till the last book store on earth operates.
Meeting someone unexpectedly. It's great fun to catch up, and as I have said before, this happens to me with students from various B schools I have taught at- some recent ones that I encountered without warning have been Vishal Tibrewal, Animesh Jain (IMT Nagpur), Jimmy Jain (IIMK), Sowmyashree Gonibeedu (PESIT), Mrunal (PESIT), Bhuvneet Raheja and Sapna Patni (IIM Indore), Viju Varghese, Shreya Sengupta (also from PESIT, different programs), ..and of course, planned ones too, like Anupriya Pandit, Sheetal Garg, Shafique and Pallavi (IMTN), Jogeswari, Savitha, Achint, Vidya and Swapna Gurijala (KIAMS), Ratnashree, Shraddha, Divya Singh, Nikita, Meghna, Manjari, Supriya, all from IMT Nagpur.
This was not a surprise, but surprising-or maybe not. I joined a music group of Hindi film aficionados thanks to a former student, and met a few for the first time, and got along very well.
Every now and then, I get a pleasant surprise in the form of a chat with a Facebook friend, and sometimes it ends up being a long one. Shreyashi (a former student now doing her FPM) is really good at these, among some others.
Comments on fb, and answers to quizzes or general questions. Sometimes unexpected, surprising, amazing etc..Oscar-style acceptance speeches too.. 😄
I listen to the radio a lot, and hearing a favourite song play is a pleasant surprise, which ahppens frequently.
Sometimes, phone calls, but since I don't pick up the cell from unknown numbers, I effectively prevent some (nasty?) surprises.