I've been a loyal oScope users for ages; I once used it as my front panel in a Halloween robot costume, and it blew people's minds that they could talk to me and have it show up on my 'belly screen'. A very useful tool indeed.

One thing that I've always wanted it to do is to be able to horizontally move/scale the frequency domain plot. Most of the time I'm using it, I only really care about the low frequency (vocal range) component.