A Chance Encounter

Here is a nifty expression for when you meet somebody unexpectedly:

これは奇遇ですね！- kore ha kiguu desu ne! - Fancy meeting you here!

Note the kanji: 奇 means strange as in 奇妙 (kimyou) and 遇 means treat or encounter as in 冷遇(reiguu) cold treatment or a frigid reception or 遭遇する (souguu suru) to come across. So literally it means "a strange encounter". Be careful not to confuse 遇 with 偶 (as I did). They look similar and sound the same but one means encounter and the second means chance.