By the wording of the question, I'm pretty sure you're using one of those pyramidal graters or a "sheet" grater.
That's great for getting the "bulk", but if you want to grate a small amount of cheese (or the last bit of a large amount, if you don't want to just eat it) then you really need to get yourself a rotary grater .
They're more commonly used for fine/hard cheeses such as Parmesan, but most half-decent ones will come with a "coarse" blade that can be used for cheddar, mozzarella and so on.
Rotary graters all have a plate at the top that lets you push the cheese down onto the blade.
Higher-quality graters will give you slightly better results; the $10 cheap ones tend to leave a mush at the bottom that's hard to grate, even if you squeeze really hard, but that's easily remedied with a small wooden block or really any object at all to put between the top plate and the cheese you're trying to grate.
cooking.stackexchange.com/users/41/Aaronut
You can turn that last quarter-inch sideways and grate until you have only a thin stick of cheese left.
If it's only going to be melted anyway, you could just crumble the last stick in.
cooking.stackexchange.com/users/77/Blorgbeard is out
I don't know of a tool, but what I tend to do is grate one way until there is only a bit left, say 2cm deep (by however long the block was)
, then I rotate the piece so it is against the grater lengthways, then grate until I have 2cm again, then rotate again so the longest side is sticking out away from the grater, and grate again.
Whilst this doesn't mitigate the issue, it does mean that you end up with a much smaller block which is ungrated, as you have grated it in each dimension until you can't get any closer.
cooking.stackexchange.com/users/210/Sam Holder
I bought a pair of kevlar gardening gloves for this exact sort of thing (and for using my mandoline without hacking off any (more) of my thumb).
With those, you can run it all the way down to the bottom and not worry about your fingers.
And when they get grotty, you can throw 'em in the washer.
cooking.stackexchange.com/users/218/Satanicpuppy
I just hold the cheese closer to the edge away from the grater.
When it gets really small
I just have a single finger on it to grate.
Though sometimes I just pop it in my mouth too :D
cooking.stackexchange.com/users/27/Kyra
Crumble it in, or just forget about grating cheese at all and just do some high-speed paper thin slices with your handy kitchen knife and block.
Tip grounded on the block, fingertips tucked in, and chop away.
By time you get a grater, mandolin, or Cuisinelf 3000 Turbomatic's fiddly little bits cleaned, you could have long since been serving up that cheese.
The knife has had about 100,000 years of R&D to get it to
it's current shape.
It really can't be much improved upon (except by a whetstone!).
BTW, it may be ugly, but some starch sure helps when handling cheese!
cooking.stackexchange.com/users/None/
You know the scenario: You grate the cheddar until you're left with a quarter-inch. What do you do? Try to grate it and risk cutting your knuckles, or pop it in your mouth and enjoy?  Usually I do the latter, but I wondered if anyone has any tips for grating cheese down to the last bit?  Is there some kind of small tool that you can use to safely grate the last of a block?
Is there a way to grate a block of cheese entirely without hurting one's fingers or knuckles?
cooking.stackexchange.com
<equipment><cheese><grating>
cooking.stackexchange.com/questions/853
cooking.stackexchange.com/users/91/JYelton
Rotary graters let you push the cheese down with a plate rather than your fingers, or kevlar gardening gloves will protect your fingers when using a normal grater. The last bit can also be crumbled directly into the mixture or thinly sliced. Try a different style of grater or a pair or gloves to protect your hand. Otherwise you could just crumble it in.
You try a different style of grater, that protects your hand, such as a rotary grater. You could just crumble it in or slicely it finely. Try wearing a pair of gloves.