What makes a standout profile for applying to a top-ten ranked CS masters in the US?
You seem to have little time to do a huge number of things, but a few things you can do:


contribute to some open source projects there are many many and all need help of at level
show that you have played with some ideas on GitHub
show you can turn your hand to many languages again stick it up on GitHub
have a shot at project Euler, and stick it all up on Github
build an App or website that does something/anything


Publications for Undergrads are great, but not really expected.