Here's some ideas:

Escape Battle - Get from one place to the other (eg bedroom to outside) by using themed punches for each room
Game Reference Battle - Use references to videogames.
Movie Reference Battle - Use references to movies.
Music Reference Battle - Use references to music.
Weapons Battle - Use weapons punches.
Concept Flipping Battle - Flip pre-defined concepts.
"Ya Girl" Concept Battle - Use "ya girl" punches.
Girlfriend Picture Battle - A picture battle of the competitors girlfriends.
Celeb Picture Battle - A picture battle of celebrities.
Random Picture Battle - A random picture used.
Personals Battle - Use personal punches.
Sports Punches Battle - Use sports punches.
Self Glorifying Battle - Use punches that make yourself look good.
Diss Yourself Battle - Diss yourself with punches.
3 Round Keystyle Battle - 3 rounds of 10 minute keystyle verses.
Cliche Concept Battle - Use cliche punches.
Money In The Bank Battle - The winner gets to face the champ at any time.
Voting Immunity Battle - The winner doesn't have to vote at the week he chooses.
Bye Week Battle - The winner gets a bye week.
Nameplay Battle - Use only nameplays.
Hardcore Battle - Anyone can write for you.