Hard for me to complain about fanservice in High School of the Dead since the entire show is centered around fanservice. The flashy zombie killing, lampshading about how 'it doesn't work like it does in the movies/anime/manga', odd camera angles, Kohta's 'crouching nerd, hidden badass' routine, the rest of the over the top character cast, random nudity, references to other zombie movies, the grimdarkness of the setting, and even the 'high speed low drag' nature of the weapons cache are all fanservice of one sort or another.
It's all so blatantly over the top that it adds a lot of entertainment value to a show that might otherwise devolve into a relentlessly grim slog.