It is an onion hoe - why it has this name I have no idea as it no more use for onions than it does for anything else. This is a Spear and Jackson one, but there are a number of different brands available. It was only cheap and I have to say it is the best thing I have bought in ages and is exactly what I have been looking for. I am not going to suggest that my veg plot is weed free, but I am more on top of weeds than I have been at this point in previous years, not entirely down to the purchase of the onion hoe, but it has certainly helped.
It works on a similar principle to a standard hoe, except of course that it is much smaller and its design means that you pull it towards you as you work. I think this makes it easier to control and less likely that you will chop down the things you actually want to grow.
I wouldn't say that I look forward to weeding, but feels much less onerous now and the onion hoe bridges the gap between hoeing with a standard hoe and trying to dig up weeds between plants.