When I was helping to clean tanks at a LFS, a tailspot blenny would charge my hand and try to bite my fingers! I thought they were cute until that experience. Of course, it didn't hurt, but I guess I am pretty jumpy and I can't help but react when something attacks my hand -- which results in a lot of spilled tank water.
In general, I'm not a big fan of blennies, because I think that they are mean SOBs. But I had a linear blenny once (not in a nano, though) that was an interesting fish -- unfortunately I accidentally killed the blenny when I removed a piece of live rock that I had never before seen the blenny on -- but that day it chose to hide within it somehow.... So, if you get a blenny, make sure you check anything that you take out of your tank, so you don't make a stupid fatal mistake like I did.