heres a couple I can throw at you:
1) make a program that takes in an equation (no variables) and solve it using the normal order of operations
2) If you are only comfortable making a console app, make a text based version of minesweeper.
3) I'm not sure how much work you've done with abstract data types (vectors, linked lists, bst's, etc) but look up some you haven't worked with much. If you've only used the STL vector, try making your own! There are tons of different kinds of linked lists, and just as many Trees. If you're really feeling adventerous, read up on Graph theory.
