I have been writing a game monography where I put together the analysis of several computer games. In order to help readers, I decided to use some punctuation marks to bring their attention to specific games. So, for instance, I decided to put a star (or just an asterisk, *, in ASCII) on the games that I consider are good, two stars (**) on games that are really good and so on. I think this is consistent on how things are rated using stars.
Now, every now and then I review a game that is really weird or unusual, even if it is not good at all. So I wanted to also bring the readers' attention to these oddities by using a different punctuation mark on these games titles. So far I have been using the tilde (~), but this is not consistent with the usual usage of this symbol.
After searching for a while I have been unable to find a symbol that is used on this sense. Probably it doesn't even exist. So my question is, is there any symbol that is used on this context? if not, what is the best way to get around it? Should I use another well known symbol by indicating what its usage mean in the text? Should I use a not widely used symbol to avoid confusing people?