I find I come across 13mm and 10mm nut sizes more often than other sizes. Many OPTs with stepped open or closed wrenches fit, though 3/8" needs to be opened up to fit 10mm, and some have 14mm instead of 13mm. An annoying loose fit. Since I also like a carbiner clip I modded this...
http://forum.multitool.org/index.php?topic=61531.msg1141340Rough cut using diamond burrs in a dremel then an hour or so with my diamond files. Given the small tool size (60mm) I don't think I have excessively weakened the tool. A great feature is that with a finger in the large opening nuts can be run up and down the bolt very quickly.
Just to summarise other changes from stock, the flat driver needs to be filed more parallel to make it work. The bottle opening function is not the world's easiest, needs a finger in the opening to lift the cap. I slightly flattened the back edge of the lifting lug to align with the bottle angle. An improvement. Optionally I made the 3mm spoke wrench 4mm (the 3.5mm spoke wrench fits my spokes but not come across 3mm spoke nipples).