Currently, I am using Lenovo X201. I am still using my 10-year-old Dell Inspiron 5150, but not so frequently.
All my personal laptops are Thinkpads, my netbook is a Google Cr-48, and my desktops and servers are all custom built, aside from the old Dell Proliant upstairs.
The best machine in microsoft windows is Sony Vaio. But if some one can't afford it then i prefer Dell Inspiron 3520/ 3521
Right now I'm with HP 4740 Probook S (i7 3632QM 2,50 GHz, 8MB, 17,3") and I like it so much. Great build quality.
Hp is good stuff. Bought their best computer some years ago (Hp Pavilion Elite 035sc) and since then I've upgraded some stuff for example RAM, Usb 3.0 PCI-express card and Raided ssds. Runs like a king!