Things I've done so far:
1. I've restarted in Safe Mode, then restarted again in normal mode.
2. Installed Onyx and cleared the Font Caches
3. Tried to identify the font in Fontbook, can't identify it.
4. Run Validate fonts in Fontbook, there are some duplicates, although I am unsure as to how to remove the duplicates, as they appear as one font in the list. Resolve Duplicates doesnt seem to do much, unless I'm not doing it properly.
After all of this the weird font is still there.