Is it impermissible to wear t-shirts that show a bit of your chest (not to an extreme, simply t-shirts that have a slightly big collar)? Or when wearing a button t-shirt, leave one button open? It is not done with the intention to attract anyone. Even though this might seem awkward but heres an example: http://www.tuccistore.co.uk/mens-1/t-shirts-polo-13/tees-vests-16/g-star-raw-mens-249947-104955_zoom.jpg
Jurisprudentially, it is not haram for men to wear a t-shirt that shows some of the chest, as long as it is not worn to arouse or attract the attention of members of the opposite gender. It might however be considered not befitting the etiquette of a practising religious Muslim man. But it is not haram.