A common but impressive mushroom I will not forget is Stropharia ambigua. It's a cold weather mushroom (September-November) and I have seen it growing all over Seattle in woodchips and leaves. The cap is cream-yellow-orange and the stalk is white. The cap is slimy/wet when young and broad/flat when mature. It has a white veil that often leaves remnants hanging from the cap margin. It can grow very tall and is usually in large groups.