Well, I used Balsamiq Mockups for a pretty long time. It is pretty solid. However, after I switched a year ago from Photoshop to Sketch, I also do all my wireframing in Sketch. There are some wireframe-ui-components out there on sketch resources or other sides.
But sketch is pretty good for wireframing. You can make your own components / symbols, for reuse. And you can export it fast to marvel or invision to build a prototype.
But often, I also use oldschool pen & paper prototypes / wireframes. Its way faster to sketch it out on paper.