Rosario to Vampire, IS: Infinite Stratos Recommendations
A harem in a school environment where the protagonist is male and is different than the rest of the school. If you like one you will probably like the other.
Both are funny harems. Rosario has 4 girls 1 guy (and I don't know about you but I never really considered Yukari to be "in the running"), IS has 5 girls one guy + the main character's older sister, who I loved.
I'd say the comedy in Rosario is a bit better, but the action in IS is far better. I preferred the IS girls over the Rosario girls too. R+V is a bit more slice of life/high-school based, whereas IS does take place in a high-school, but the story is more concentrated on the action.
I also preferred the protagonist in IS (Ichika) over Tsukune.