I would say a second hand T420(s) T430(s) or equivalent. There are plenty of them due to companies renewing their stock every once in a while. I got mine (T430)

I would say a second hand T420(s) T430(s) or equivalent. There are plenty of them due to companies renewing their stock every once in a while. I got mine (T430) for 300€ whereas it sold new for 1200+€. I had a T420s before. It sadly died falling from a window. They are quite sturdy laptops of professional grade. EDIT: I'm talking about the Thinkpad brand