Well there's
Polymanga in Switzerland (French-speaking Switzerland that is) every April that no one seems to have mentioned.
And what's with the Wiki article ? Some of the conventions mentioned here aren't on the page, so I suppose they were taken down because there wasn't any main article. Do you want us to write the articles for the cons we list ? If so I'll gladly do so for this one.
And, whilst I'm at it, it's quite surprising that the page isn't available in any languages other that English, French or Portuguese, the latter two of which aren't particularly complete (the
french presented it in a table which, albeit ugly, is quite practical).