For me.. its Spitting Spider... why?
I remember when i was 10-11 watching my brother play Mir and i saw him running up from Ginko, to that little fenced area where there was a spitting spider, and he died... I then had a go for 15minutes, i ran and attempted to kill this spitting spider, eventually giving up. This is my most treasured memory of playing Mir with my brothers... as we all stood watching each other.