More than most series, this is a really, really tough question, as I love literally all of the characters for different reasons.
But as I'm watching the first OVA, when I hear this line
Fujisawa: Oh no! Someone else has run out of alcohol too.
it was cemented in my mind right then and there: I'm a Fujisawa fan.
It might sound tacky, but I legitimately find his character inspiring. He clearly has more than a bit of a dependence on alcohol, so the way he's presented as having a honest to goodness superpower when he refrains from booze is the show screaming at anyone in a similar situation "look at how much potential you have!"
Fujisawa's an old dog, but even he learns something new about himself on his trip to a faraway world. Despite his hilarious admission "I'm weak!" when we're introduced to him in school, on El-Hazard he begins to learn that sort of thinking is just a mind set. It's a lesson for anyone, be it alcohol or anything else: when we master our own habits, our potential skyrockets, and if you're a slave to a non-productive or undesirable behavior, with the support of others (thank you Miz) and the right mind set you
can master it, it's just up to you to choose whether you do or don't.