Certainly not Fashoda since France could not stand a conflict agains the UK at that time. Such a conflict would have led to an alliance between 2 powers bigger than France : the UK and Germany.
But if you want a massive conflict in the 1890's, you should think about the alliance between France and Russia. What if Germany had considered such an alliance an intolerable threat to its security ? However I think this would be too soon. Things need to mature.
So why don't you go towards some kind of uprising in Alsace-Lorraine. People no longer want to be a reischland under the german rule. The german government reacts so clumsily that the majority of the people revolt and ask to be reunited to France.