ok so i made this last night and it turn out really well, this is not my code. this is the Vombie from the animals mod, modified further, he has more aggression, hits way harder, and has a different pattern than zombies. they will occasionally jump to get up stuff. they will attack you if your not paying attention you'll get mauled. i play with item drop on death so im very weary^^ i did this after realizing there nothing that really presented a challenge to kill. i would really like this mod to evolve into something that the nether can work with, maybe the enderman could drop nether pearl (much like minecraft) and make this a requirement to make a portal. Like the end portal in minecraft.
Screenshots
EnderFreaks 
enderfreak phase shifting back into the ender dimension because the UV rays of the sun disrupt his molecular structure:D

GET IT!-
http://www.mediafire.com/?dnrddloblisd5oalicense-gplv3
and again this is not my code just a modified mod^_^
THIS WILL NOT WORK ALONGSIDE VOMBIES!!!