One of the handiest things I've bought recently for doing your nails has got to be this nail polish remover dispenser.
Okay, it doesn't help you do your nails, but it does help you clean them up if you make a mistake!
I bought it off of eBay (as usual!) for a mere 99p with free postage. It took a little while to arrive because it came from China, but it's worth it!
It's a very simple idea. Just like a pump dispenser on hand soap, but instead of the liquid coming out on your hand, it goes straight onto the cotton pad.
There's no mess and not a chance you'd knock the tub over and get stinky nail polish remover everywhere.
I'd definitely recommend getting one if you change your nail polish often.