In Zelda: Phantom Hourglass, the last heart container on your health meter flashes on and off constantly. It never stops. If your health bar is full, it's flashing. If you've taken some damage, it's still flashing. If you're almost dead, an incredibly annoying siren sounds comes on and cannot be shut off.
I could not finish either of the first two Splinter Cell games because of the reminder bar for your objectives. If you stopped moving for literally two seconds, a bar would pop up on the bottom of the screen, reminding you of what you're supposed to be doing. If you started moving again, it would go away. Since so much of Splinter Cell revolves around waiting, the games basically featured a billboard that constantly appeared and disappeared on your screens. Again, this drove me bonkers, and instead of actually finishing what appeared to be good games, I had to stop playing them.
Fighting games are also pretty bad for me. It's 2007, now. If you're porting your arcade game onto a home console, there's no damn need to have a constantly flashing "Press Start to Play!" reminder above the 2P life bar all the time. These things are constantly flashing and cannot be turned off. Why? Is there a single fighting game fan in the entire world who doesn't know that they can press play to hop into a game? Do we need a constant reminder of this? Does it need to always be flashing on and off?
For the life of me, I can't figure out why otherwise smart game designers persist in making games that have constantly flashes elements of the HUD or UI that cannot be turned off. I'm sure it doesn't bug most people, but it really, really annoys me when I have to play a game that has something like this in it, to the point where I will give up on decent games simply because I can't stand to look at it anymore. Seriously, if you're playing Phantom Hourglass and need to have a flashing heart to remind you to look an inch away from the middle of the screen to check your health, then you're probably two years old and don't have the hand-eye coordination needed to finish the game anyway.
I'm not epileptic or anything, and I'm fine with having flashing warnings on the screen if they serve some kind of purpose, but when they're patently purposeless (the objective bar in Splinter Cell was totally unnecessary, since you could check your objectives on your PDA at any time) and can't be switched off, then someone on the design team needs to be fired.