You thinking of GC2Converstaions? (What else?)
Just out the top of my head, Techtree.xml, Events.xml, UPIssues.xml, PlanetImprovements.xml, StarbaseModules.xml & InvTactics.xml - basically everytime a line specifies a value which is already the default value if no actual value is defined at all.
For example, in Techtree.xml (ONLY the general Techtree.xml, not the individual techtree-files)
or if one tag logically prevents another tag to have any effect at all, for example:
Ofc the other files have different such taglines, and some files do have a lot of non-working tags specified as well.
I've removed all those entries for FW but don't feel like doing it all over again (well, let's just say that the possibility is there that whatever we do currently will never see the light of the day, indeed even the former version is already 3/4 of a year "en route" and still not delivered. Anyway, last time it took the same amount of time and was upped (IRRC) before New Year's Eve so let's see if history repeats itself...)
What's your stance on techtradeing - is it too difficult to get technologies? One thing I've noticed is that the CU did increase alot of AIValues by quite some margin all the while even reducing the WillingnessToTrade-value, both tags mutually influence each other. For FW I've made a complete comparison of WillingnessToTrade (which was specified oftentimes, and differently, in the individual races' techtrees instead and lots of their values were far bigger (=favourable for techtrade) than it now is. Basically whenever no value was present in Techtree.xml someone just took =50 by default ignoreing the vanilla values, and in a lot of cases values have been decreased by alot in order to make techs very hard to get (eg. generic influence). I found little to no occurrence when values were adjusted to be more favourable for tradeing...