@Metaru - the one he went with actually looks more like a W to me than that one... although it's pretty close the the H. Below 5 pixels, fonts are necessarily sort of illegible, though... pretty sure there's no getting around that.
Nice, small fonts are always hard. I tried a 3x3 and it was definitely a challenge. half of mine came out a mess. great job!
I guess that could work, but it looks more like a V or U to me. If it was 5*5 and not 4*4, these things would be so much easier! 
It's always a challenge to create something with meaning in such a small space... Thanks for the comments everyone!