Formal:
* Cela m'agace. (This is a very neutral and polite way to say it)
* Cela me gêne. (This implies that it's more of a nuisance or inconvenience)
* Cela me contrarie. (This suggests a stronger feeling of annoyance)
Informal:
* Ça m'énerve. (This is a more common and direct way to say "it annoys me" and can be considered slightly stronger than "agace")
* Ça me fatigue. (This implies that you're tired of it)
* Ça me gave le bourdon. (This is a very colloquial way to say "it gets on my nerves")
More specific options:
* Cela me met hors de moi. (This means "it drives me crazy")
* Cela me rend fou/folle. (This literally means "it makes me crazy")
The best option for you will depend on the context of your situation and the level of formality you want to use.