Another vote for Neutrogena Helioplex here. I don't find it too greasy and with my oily skin, I only have to re-apply it once a day, if I'm out in the sun all day. Most people should reapply it every couple of hours, though. It doesn't seem to make me break out at all.
Something I found interesting... I have some friends who live in California. I ran out of sunscreen when I was down there one November and went to buy some more. It was somewhat difficult to find. Apparently, sun screen is a seasonal item. In California. What?!?!?
I can't wear a hat, for the most part. Either it doesn't fit or stay on my somewhat weirdly shaped head or it holds in so much heat that I feel like the top of my head is about to pop off. So I wear a visor when I'm outside in the summer. Which has the added feature of fitting under my hair and keeping it off the back of my neck. But it means that it is very, very important to remember to put sunscreen on my ears!