I can name quite a few:

Megaman 8. This is proof enough as to why:
MM: "Where is Dr. Wily?"
Light: "Dat's a good kreschun. We may-ay be abuh to wocate enudduh enuhgee emission fwum da wadaw woom.....When we fine dat meteuh, we'w fine Dokta Wawy!"



Megaman X7. Axl and the bosses just sound HORRIBLE. The worst offender is probably Flame Hyenard, though.

"BURN! BURN! BURN TO THE GROUND! BURN! BURN TO THE GROUND! YAHOOOOOOO! BURN! BURN! YAHOO! BURN TO THE GROUND!"

And you have to listen to that for the whole battle. Ick. Vanishing Gungaroo is probably the second worst.

Shenmue, as someone else pointed out. Could Ryo be anymore stilted?

"I see....."

And then there was that Lucky Hit thing. "Would you like to play a game of Lucky Hit?!" "Do you wanna play Lucky Hit?"

Brave Fencer Musashi has okay voice acting, but some of Rootrick's lines crack me up so badly!

"Haha! Y'ALL BEEEN FOOOOOLED!"

"Shaddup ya dumb gal.....or else y'all gon' get a lickin'!"



And the final one I can think of right now, Star Ocean 2. Most of the voices in battle were annoying, but Precis takes the cake, runs with it, falls over on top of it, and then eats the smushed remains of it from the pavement. Her mangling of "Parabola Beam" especially just drives me up the wall. It's not pronounced "pair-uh-bowl-ah," it's pronounced "puh-rab-o-la!" Get it right!