BIKEHAND YC 271 Chainring Nut Wrench
This is one of those tools that you don't know you need until you try and remove the chainring bolts from your crankset.
The business end of this one holds the back of the chainring nut whilst you remove or tighten the bolt with a hex key from the other side. Using this tool will save you many tears of frustration and get the job done without damaging your beautiful crankset (and without stabbing yourself with a wayward screwdriver).
One end for small chainring nuts and the other for slightly less small chainring nuts.
In addition you also get a 9mm & 10mm wrench.