Playing Sonic '06 - biggest [tornado fang]ing mistake of my life.
I don't think I've ever played such a horribly broken game in my entire life. And I've played very broken stuff.
One of the biggest examples, is that one mission, to put apples inside baskets.
...that is most probably the VERY WORST gameplay-to-objective relation I have ever seen in any commercial game, ever, ever, ever. It just doesn't work, but it doesn't work in such a horrible way that it reaches paradoxes of unworkeability.
...also, using the homing attack on rocks to light them up, and the rocks basically behaving like walls and getting you to bump into them when you did attack them requiringly.