1.) In Life Serial, When they were both getting drunk (or maybe it was just Buffy...)
2.) In All The Way, After the whole fight scene, Buffy stoped Spike from leaving her house to say Thanks.
3.) In As You Were, In the beginning behind the tree, she kind of smirked at him...;)
4.) In Flooded, He knew he could get a grin...
5.) Under the rug, in the beginning of Dead Things, they both smiled at each other :)
6.) Gone, HEY! They must have smiled at each other, we just couldn't see Buffy doing it :p
7.) They both smiled at each other during Hell's Bells, when they relized they didn't like being apart.
8.) In Older and Far Away, they smile at each other when they are in the hallway.
9.) He smiled at her in Afterlife, when he sees that she is alive.