I just discovered something. Pick Lulu when one or more of the following champions are on your team:

So I recently discovered that the combination of an on-hit building Kog'Maw with an Ardent Censer Lulu was played extremely often in Korea, but only if the two are together. Since I believed both Kog'Maw and Lulu to be mediocre and was therefore really confused how they just suddenly came back, I went to investigate. What I found is just short of being insane.

A Lulu combining her Passive, her W and an Ardent Censer will give an ally that you cast your abilities on up to 152 ( + 15% of your AP ) magical on-hit damage, 35 on-hit heal and 80% attack speed. That's 6675 gold worth of stats, plus 0.6 for every point of AP. This is BONKERS!

And that's not even counting the movement speed portion of her W and the rest of her kit. If you combine that with any champion that is an on-hit carry, you will amplify their damage by a huge amount. Kog'Maw undoubtedly works the best since he's the most on-hit and attack speed centric marksman in the game and will be near Lulu from the start, but combining it with any of the others that you can see above is really damn efficient too.