Gandalf (LOTR) vs. Harry Potter (HP)
Gandalf wins by a landslide. While Potter has a wand, Gandalf has a whole freakin' STAFF! ... and he can grow major facial hair.
Legolas (LOTR) vs. Dobby the House Elf (HP)
Dobby's off to a strong start. He deflects all of Legolas' attempts with his own House Elfy magic. Legolas strikes again, but his long blond hair gets in his eyes. He is distracted by his reflection in a puddle, giving Dobby the momentary advantage. But the H-E never was very good with sharp, pointy objects. Watch out for that arrow, Dobb--Ooh. Not pretty. Legolas wins... by a hair ;)
Orcs (LOTR) vs. Inferi (HP)
For a first, I think HP's world would win. While fire or heat hamper Inferi attacks,
and only sunlight can slow Orcs, Orcs can be killed. Inferi? Well, they're already dead. Hard to destroy something like that without magic, which Orcs don't have.
Gollum (LOTR) vs. Severus Snape (HP)
What? They're both pale and greasy and like dark places. Anyway, Sevvy would win with sheer wandage powerage (Avada, anyone?) Though I think Gollum might try to eat him first and give it a fair attempt...
Balrog (LOTR) vs. Hagrid (HP)
After Hagrid tries to make the Balrog a pet (Aww, the lil' tyke) and fails, the Balrog decides he does not like being called "Bessie" and sets the half-giant on fire.
Worm Tongue (LOTR) vs. Lucius Malfoy (HP)
Both cunning in their own oily ways, the two make fast friends and live in mutual hatred of each other. Everybody loses.
Sauron vs. Voldemort
Both evil with no apparent reason (mommy issues?), both not entirely alive or dead, both with life forces tied to earthly objects, these two wizards would have to find each others rings/Horcruxes and destroy them. Voldy has seven. Sauron has one. Both have many obstacles set in the way, along with loyal followers.
And the winner is...
I can't say without a certain side killing me, so I'll just leave it at that ;)
Who do YOU think would win?