I was thinking about the mice and what unbelievable leapers and climbers they are, and thinking that watching skilled mice fight would be like a wire-work movie at double speed.
Falling speeds would be proportionately much higher than they are for people (think of the slow way in which giants or buildings topple, for mice it would be the opposite). A person falls about two and a half body lengths in the first second they fall; a 3" tall mouse would fall more than 60 times their height!
And yet, because of the much higher strength of materials at those small scales, they could that huge distance and be much less hurt than the human - you could be thrown of ‘bridges’ and not get seriously hurt. (Accordingly, mouse bridges could be pretty damn precarious and very high up and be culturally acceptable.)
I think that opens up some really cool Indiana Jones-type scenarios. Mice could feasibly survive the destruction of a twine bridge strung up between trees when it’s attacked by squirrels or a hungry crow.
Mice wouldn’t need cups; they could pass water fist-sized droplets around on flat ‘drinking plates’ as the surface tension would hold it up like a sticky water balloon! Bottles would be downright problematic.
For similar reasons, mice would have a hard time generating enough momentum to hurt one another as badly with weapons- biting would be proportionately more significant. Even soft fur could be very effective armour against a 3-gram axe. Bird feathers, with all those fibres laying across one another, might be practically impenetrable.
I suspect piercing weapons would be very useful at those scales, especially those with poison! (Get your local Apiarists to abduct some bees and Science yourself up some bee-toxin weapons - fend off predators with some kick!)
Ooo… imagine the predators attracted by a large-scale mouse war? You’ve been in the thick of battle for twenty minutes when a pair of coyotes appears. Suddenly both sides are scrambling for cover, up trees, into holes - and it’s mayhem as both sides find themselves completely commingled in their hiding places.