Hi,

I have never played a Paladin before and I am looking to do one but I have a question on the Shield master feat. the 2nd bullet.

• If you take the Attack action on your turn, you can use a bonus action to try to shove a creature within 5 feet of you with your shield.
• If you aren't incapacitated, you can add your shield's AC bonus to any Dexterity saving throw you make against a spell or other harmful effect that targets only you.
• If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect.

Dose this work on a Fire ball / Dragon breath that hits me and no one else. I don't think it dose as the bullet says targets only you.
then I thought FB and DB don't target anyone right, there just point and click spells. so would I add my Dex + my Shield AC from this feat to save vs these  ? 

Can you tell me what kind of attack, spells that make you take a Dex save but would not let you use your Shield Master feat vs ( I don't needs lots just an idea of what would stop it) 

Hope I made sense on this question.

This feels like a DM ruling kind of thing. 
Personally, I’d say something like a fireball doesn’t target “only you” it targets a point in space. It might happen you are the only creature in the radius but that doesn’t make you the target. I could see other DMs being more charitable.

Still, if you make your save, the third bullet still comes up, so you would take no damage on a save.

There is some debate about this because WotC uses the word “target” too often, too loosely, and for too many reasons. In general you’re gonna likely hear 3 main answers, but only the 3rd one really matters in a practical sense:

1. No. For a spell to “target only you” it must be a spell that either only targets one specific creature, or that targets a number of specific chosen creatures and you were the only one targeted. Since an AoE like Fireball targets a point, not a creature, and affects an area, not “creatures,” it doesn’t count for this.
2. Yes. If you are the only creature affected then it applies.
3. Depends. Talk to your DM and find out what they say.

Of course the fireball spell would still come under option three here. But you wouldn't get the dex bonus. 

• If you are subjected to an effect that allows you to make a Dexterity saving throw to take only half damage, you can use your reaction to take no damage if you succeed on the saving throw, interposing your shield between yourself and the source of the effect.

According to the Dev, a Fireball doesn't qualify you for Shield Master's 2nd bullet. https://twitter.com/JeremyECrawford/status/897558230745976833?s=20&t=3N6t_CTjhbeTwnNTDxqeKA

@JeremyECrawford The rules on spell targeting (PH, 204) do mean that you can't use the 2nd bullet of Shield Master against a typical AoE.