Speaking from personal experience (unfortunately), I have used Neutragena Ultra Sheer cream with SPF 100, also SPF 70 on my face and ears. Not had a single sunburn since using it. Usually only reapply once while out.
I use Neutragena Beach Defense on my neck and body with the same results.
Key to applying sunscreen: make sure that you do it about 30-60 minutes prior to going out. Most people wait until they are already outside, and sweating. Makes that first application less effective. I believe that the key is the first application soaking in pre-sweat…
Even with the high SPF, I still get some tanning. I know someone is going to comment that higher SPF sunscreen is only incrementally more effective than 30SPF. While that’s true, if it keeps me from burning, then it keeps me from getting more skin cancers down the road. Every little bit helps.