Torn between the beautiful clois proposal with all those petals and right by their phone box and the door scene in the finale. Both are so amazing to watch.
For me, the best moment in season 10 was in episode 4 at the end when Lois and Clark are dancing in the barn and Clark finally lets everything go that was keeping him from being the hero his was destined to be. Not to mention they both say "I Love You" for the first time.
The first time clois says I love you to each other
when Clark asks Lois to Merry him.
The first time they make love
Their wedding vows
and any moments with clois together