I thought of these 3 just earlier today, playing Split/Second.
1) AI drivers finishing in the exact same (or almost the same) places EVERY TIME if you aren't there to mess things up a bit - or in some games, even if you are . It makes it harder to stay at the top in a series of races - if you don't win every race, the AI who always got 2nd behind you will probably overtake you on points, and if you get in the bottom half it'll be impossible to catch up again. OK, so all you'd have to do to win without this flaw would be to finish in the top half consistently and the AIs would average out at halfway, but either compromise and have them finish within 2 or 3 places of their usual spot (simulating individual driver skill and bad/good days for that driver) or make them all better (so it's harder to even finish in the top half). Or, give them each their own personality (aggressive, dodge-happy, come from the back of the pack etc) that is suited differently to different tracks or modes. This gives an added benefit to players - you can learn their personalities and learn how to counter them. Perhaps you could even program the AI to do this.
2) If you pick a bad car, the other cars are also bad. It makes it easier to win the crappier your car is - you'll still have the same advantages/disadvantages your personal driving skill/style brings, but with slower cars you have more time to react to danger - you have an advantage over the AI that is taken away with faster cars. As an example in S/S, I can win almost every race with the all-round Class C car, but I struggle to place 5th with the all-round Class A. Your opponents should have preset cars for each race or series, to force you to upgrade to keep in line with them.
3) Redoing races when the story dictates that's impossible. S/S is meant to be a TV show - how can you possibly redo those races if you don't think you did well enough? Tell the viewers to wait while Mr. Unsatisfied has another go? Take a leaf out of most other genres' books - if you do well enough, you can't redo it. If you didn't do well enough, you have to replay the entire series/season/whatever again. This encourages you to practice races beforehand, so you can do very well in the real thing, if you get rewards for doing so. Performing OK won't give you those rewards, but will mean you can't try for them again (at least until the endgame).
Other games:
Enemies with a telepathic link. There are several things related to this - if you are discovered, every enemy knows where you are, if you kill one with some kind of stat attached (e.g. belonging to a faction) it causes a global effect (decreases your allegiance to that faction) immediately, and others. Fair enough with radios or enemies within earshot, but what about, say, Oblivion? You commit a crime in Bravil, ride as fast as possible to Chorrol, and everyone there already knows about it. I can't remember if they actually did in Oblivion, but the general point stands.
Hard-to-see enemies. Anyone who's played a shooter knows about this. You're getting shot at, but you can't see where from. So how do you find out? Get hit, and the damage thingy shows you what direction it came from. Can't there be another way? I can't think of a reliable way, but I'm not in the games industry. Surely those who are can find a way.
I could go on, but those'll do.