If you liked the MM! anime, the Anime-Planet community thinks you'd like:
Ayumu was murdered by a serial killer – at least, he was. For after the mysterious Eucliwood Hellscythe revives him, he changes from a human to a zombie, much to his dismay. Now, in addition to being unable to die, the boy must see to the whims of his supernatural, silent companion – but things continue to get worse from there. As once Ayumu accidentally steals a magical girl named Haruna's powers, he is tasked with the embarrassing, obnoxious task of being a magical girl – err, boy – in her stead! Then with the addition of a hostile vampire ninja to his household, can Ayumu manage to maintain his new home life, fight against attacking monsters, and track down the person who killed him all while attempting to keep what little dignity he has left in tact?
Kore wa Zombie desu ka? and MM! are both about a guy in a weird predicament. They both are surrounded by girls with a variety of personalities, tsundere and sweet. The guy always is insulted, being called a pervert and is continously bossed around.
Keitaro Urashima is somewhat of a failure. In order to fulfill a promise he made to a girl fifteen years ago, he has tried time and again to get into Tokyo U but has never managed to pass the exam. However, fate smiles upon him and he ends up working for his aunt, managing an all-girls dorm! Living with the feral Kaolla, the timid Shinobu, the sake-loving Mitsune, the blade mistress Motoko and the punch-happy Naru, can Keitaro keep his focus and keep his promise? And will he ever end up meeting that girl from his past?
Having lived in the same orphanage as children, Takumi Tsuzuki and Fumino Serizawa grew up together and remain fast friends. Now living and working at a bakery, Takumi does his best to prevent catastrophe, particularly when the clumsy Otome is in the kitchen! He attends school with Fumino and is still the only person capable of reading through her baffling habit of hiding her emotions by saying exactly the opposite to what she means. However, the arrival on the scene of enigmatic catgirl Nozomi may force Fumino to be more honest with her feelings than she is used to - or perhaps even able to. This, along with a host of crazy friends and associates such as the stuck-up Chise and the otaku Ieyasu, ensures that there is rarely a dull moment in their lives!
The main similarity with both anime is that the girls all like the main guy, but the guy is clueless about it. With some not honest with their feelings and others very open about it, it is very hard for even the viewers to choose who he should be with. Also, another similarity is that the main character keeps getting hit by the tsundere girl, only in MM! he enjoys it more.
If you liked MM! then there is a chance that you'll like Oniinokoto (and vice versa). Both feature a cast of unusual characters and don't hold back on sexual allusion, definitely not one for kids. Another comparison is the cast's habits, all of them are unsual and not usually seen in recent animes. Overall how ever Oniinokoto seems like it will be far more ecchi than MM! but both seem to be worth watching. So if your in the mood for some different why not watch either one of these?
Kyousuke Kosaka is a normal teenager with average grades and an average home life, but when he finds out that his overachieving younger sister Kirino has been hiding her vast anime and eroge collection from their unassuming parents, his world turns inside out! Now, having promised to help his formerly distant sibling navigate her two distinct lives, Kyousuke finds himself drawn into Kirino's world of magical girl anime and "little sister" fetish games while covering for his sibling to her parents and friends, not to mention trying to provide what guidance he can.
Both are comedy anime and the female leads are tsundere characters with blue eyes and blond hair, they even have the same seiyuu. If you haven't seen Ore no Imouto yet then I warn you that Kirino (the female lead) is extremely annoying in my opiniom throughout the whole series.