Anko. They seem best suited for each other. Both have a laid back attitude and are strong. Shizune doesn't have a similar personality, Kurenai is completely out of the question (haha), and Tsunade is, what, 50-something now? She's great looking with her fake appearance, but we all know from the brief one-shot of her wrinkled hand in the Tsunade & Jiraiya vs. Orochimaru fight in the manga that she's older.
(A lot of people ship Kakashi and Sakura, but the age difference is too monumental.)
Spoiler Alert! Click to show or hide
Despite this forum post I am sad because we current readers know that Kakashi will never get to be with anyone. . .since he passes away. I am sad just thinking about it.