I took the feat Weapon Finesse with a rogue. I later on multiclassed into Swashbuckler which gives me Weapon Finesse for free at 1st level. What happens with the feat I already have?
Is there a way to retrain feats? Can Weapon Finesse stack in any way? (I haven't found one, just making sure.)
My DM won't let me remove the feat since he has already denied others.
You cannot generally select a feat that you already have, but if you are granted a feat you already have, you end up with two. Unless the feat has a Special section saying that it stacks with itself, it does not. Weapon Finesse does not say this, so the two copies of Weapon Finesse are redundant.
The Player’s Handbook II has retaining rules you can use to replace the Weapon Finesse you originally selected (not the one from swashbuckler, as you had no choice in that one). This can be quite expensive and time-consuming, depending on how long ago you made this choice, and you will need your DM’s support to use it.
Psychic reformation allows far quicker and cheaper retraining than PHB2’s retraining rules, but you have to find a 7th-level psion or wilder who knows it in order to use it. If you do, hiring him or her to manifest the power will cost you a minimum of 530 gp. Alternatively, a power stone of psychic reformation costs a minimum of 950 gp. That can be activated by any psion or wilder (with a relatively easy manifester check if they are below 7th level), or anyone who can make a DC 24 Use Psionic Device check.
In both cases, the service or the stone will cost an additional 250 gp times how many levels ago you selected Weapon Finesse the first time. For example, if you are level 5 and chose Weapon Finesse at 3rd level, the service will cost 1,030 gp, and the stone will cost 1,450 gp.
Again, this cannot replace the Weapon Finesse from swashbuckler; it only lets you remake choices you made in the past.
Embrace the dark chaos replaces any feat you have (e.g. including that Weapon Finesse from swashbuckler, or even more ridiculous things like the weapon proficiency feats from the elf race) with an Abyssal heritor feat.
Shun the dark chaos allows you to replace any Abyssal heritor feat you have with any other feat you qualify for.
So you can embrace the dark chaos and then shun the dark chaos to swap any feat for any other feat. This is a broken, theoretical-optimization trick known as the Dark Chaos Feat Shuffle, or DCFS for short, and is not recommended in a real game. In any event, both are 8th-level spells that cost 250 XP, so quite expensive compared to psychic reformation (but far more flexible).
In my experience, it is extremely common to insert the words “If you already have [feat you would gain as a bonus feat], gain any other feat you qualify for instead.” The only official use of this sort of thing to my knowledge is the marshal from Miniatures Handbook, but it’s a good idea that eases headaches and somewhat reduces the need to metagame-plan your character out ahead of time.
I strongly recommend you ask your DM for this option. It’s fair, and improves the game.
The Player's Handbook II includes a chapter on rebuilding characters (p. 191).
Replacing feats is considered "small-scale" and the chapter suggests that simple retraining is enough - done in the background during downtime for instance.
For rationale, a short quote (p. 192):
For players and DMs who are accustomed to treating character creation and advancement decisions as permanent, the idea of character revision can seem strange or daunting and some might even think of it as a form of cheating. Such reactions are natural, but if you think about it, normal people “revise” their abilities all the time.
In the end, all depends on your DM (and other palyers if they were denied this opportunity).
Feat Descriptions in the subsection Benefit says that
If a character has the same feat more than once, its benefits do not stack unless indicated otherwise in the description. In general, having a feat twice is the same as having it once. (Player's Handbook 89).
However, a generous DM may allow you to use the retraining rules (Player's Handbook II 93) to swap out the now-obsolete feat.
Officially you would be stuck with a doubled feat that is redundant. House rules is how I usually deal with this.
I have this question come up all the time. While some people prefer to try and plot out the course of their characters development ahead of time, many of us aren't that far sighted.
In another case your tastes could change and the turns you have taken for this character divert away from what you originally planned. Or the 'this would be cool' sets in. Regardless of how it happens out, I am a staunch supporter of the retraining option.
If it makes sense and you meet the prereqs move further along that feat tree, if not take a different feat that you qualify for, that compliments the feat/class feature in question. This is another one that comes down to how kind is your DM? However I only allow this option during down times, when it would make sense that the character could work on their abilities. Training halls, Adventuring guilds and combat specific trainers would be the avenues that I would use to try and retrain my hero.
