I've read a fair amount of romances, lately. And, while some were truly interesting and unique, many fell back onto the same plot devices or clichés. I am beginning to detest the repetitiveness. *Note: I'm not stating these should never be done again, but should be done well and with a compelling slant.*
Love at first sight - Is one of your characters from Disney? No? Then it's lust, not love. Make the characters work towards it. It shows who they are as individuals. The payoff for the reader is greater.
The love triangle - Ugh. Because a heroine can't be hot enough, loved enough, or dramatic enough, unless two people want or love her. (Notice most triangles are two men fawning over one woman.)
Alpha males and helpless females - It doesn't matter how strong-willed, self-possessed, or skilled our female started, she's going to need the bulky arms and warm shelter of Rambo/Dirty Harry before too long.
The witchy "other woman" - While not necessarily an ex, this secondary character wants to cause hardship to either the main couple's relationship (a mother thinking one protagonist isn't good enough), or the heroine directly (a co-worker trying to steal away a promotion).
Cheated on - Almost exclusively to the heroine (especially if it happens at the beginning), this event makes her unable or unwilling to trust again.
I know this happens in real life, a lot, but the authors beat the same ground.
The misunderstanding - because, of course, a character can't spend two minutes asking for clarification or hashing it out. No! Better to throw away the person he/she swore was the one without further evidence or communication.
The secret baby/pregnancy - exclusively to the hero (of course). He gets a visit from an ex (or casual fling) stating there was a child he never knew about. Many times, this is used as a plot device to throw the current couple's relationship into chaos, but can also serve to "change" a difficult man or playboy into someone respectable.
At times, the heroine will also hide a pregnancy because of the hero's possible reaction.
But a baby always makes things better... eventually!
Well, that's it for my list, for now.
Do you have any you'd like to add?