I went to Oktoberfest with my family! My husband also bought me a cute crystal nail file for $6 at a nail art stall there. It files like nothing else I've ever tried. At first I was like, "Woah? Where the hell is the grit? How is this going to file my nails?"
Then I tried filing. Magic ensued. The edges of my nails filed down evenly and without splitting. The tips were very smooth, not the usual ragged ones I got with my metal file. I barely had to apply pressure at all! The best part about this is it supposedly will never wear out, since it's glass. The bad part is I like bringing my nail files with me, and it doesn't come with a case :( I stuck it in my camera's pocket instead, and surrounded it some business cards.
Sorry my post isn't as long or informative as it usually is (kinda xD).