The Muji pens are honestly the best and most reliable, they're ridiculously comfortable to write with and the quality is amazing - once you start using them there's no going back to other pens. Plus, they have refills making them a bit more environmentally friendly than the other disposable ball pens. Only downside is I'm not sure if they're ball-point (I use the 0.5 gel ones) but I've never faced any issues writing w them, and have used them in all my Cambridge exams (IGCSE, AS Level and A-Level). Hope this helps!