Mind I dont pay attention to power builds and I dont play the game fast.
But so far for me:
Tier 1: Near musthave if its for your build
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Lucky - Basically another Lore Bard or Divination Wizard, except it works out of combat as well. Awesome.
Polearm Master - Second best warrior feat and friggin awesome.
Savage Attacker - Ironically despite the name actually a musthave for Paladins, since it works on their Smite spells, too.
Spell Sniper - Musthave for Sorcerer and Wizard so they get twice as many crits and access to Eldritch Blast. Always my first pick for them.
Tavern Brawler - Best warrior feat and also friggin awesome. Only one in group can really fully benefit though because you want the itemization, too.
War Caster - Musthave for Sorcerer and Wizard, unless you can avoid concentration spells.
Tier 2: Solid picks if its for your build
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Athlete - If you want +1 Str on an offensive warrior, such as mainly Barbarian, this is probably the best pick. Its still not actually great but its solid enough, I think.
Great Weapon Master - Really solid choice, but it occupies the bonus action, which all too often was already used for jumping. Extra damage for easy to hit targets, too.
Heavy Armour Master - Nice to get +1 Str and max out a defensive tank. Does one need a defensive tank ? Given we only get four peeps max, the best defense seems to be offense.
Mobile - Pretty useful if you want to move around a lot. For example because you have a ranged build.
Sentinel - Pretty good. Especially for a defensive warrior. Only one in group should have this, since Sentinels cant protect other Sentinels.
Sharpshooter - Kinda good if you go ranged, though mostly for the a damage for easy to hit targets.
Tier 3: Mostly roleplaying choices
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Actor - I pick this for protagonist Bard, but mostly for roleplaying reasons. If you dont actually have other social skills on Expertise and also have Charisma without end, and arent the protagonist, I dont really see the point. Both Persuation and Intimidation are more important than Deception, and Perform is even more rare. Well, usually.
Alert - I'm always tempted by this on warrior, especially if they have Heavy Armor and Dex 10. Tough opponents can oneshot you and with this you can oneshot them instead.
Elemental Adept - Might pick on a Storm Sorcerer or some such build for roleplay reasons, otherwise I dont see the point. Only really helps with opponents with resistance. Non resistant opponents show no change, neither do opponents with immunity.
Mage Slayer - Great, but too much other good stuff around. Roleplaying choice for a Paladin ?
Resilient - Great idea but theres just not enough feats, so I mostly go for roleplaying for this. If you pick this, probably go for one of the primary saving throws you're missing (Wis, Con, Dex).
Shield Master - Another roleplaying choice for Paladin, to be an even better magekiller. Though ironically Paladin doesnt really get good Dexterity saving throws.
Tier 4: Probably not ... ?
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Ability Improvement - Honestly kind of meh. I mostly really pick this one for roleplay reasons. Or maybe to even out two odd ability scores.
Defensive Duellist - Decent. But really, if you want all defense, go Heavy Armor for the damage reduction.
Dual Wielder - Does too little for wasting a feat on this, unless you have an itemization argument to make.
Magic Initiate: Class - I think this is a waste, but what do I know. Yeah there are some nice ideas, but there are just too many other good feats around. Really the main problem with this is that level 12 doesnt give you more spells. So why not take a level of this class instead, whatever it is ? Very likely much more benefits this way than taking this feat.
Tough - If there is really nothing else good to pick for your build, this is often a very solid choice. But really even at maxlevel you only get 24 HP.
