My memory's usually pretty good, but... (Destiny)
For some bizarre reason, I can't seem to internalize the three Champion symbols. (Well, two of 'em. I'm okay with Barrier.) When I see the symbols for Overload or Unstoppable, even though I've been shooting (and spec'ing for) Champions for a couple of years now, I have to check which is which. Yes, I know there are only 2. I don't know why it's such a tough thing for my brain.
Over on Reddit, u/totnac put together a simple graphic - I think it helps.