The other thread about useless spells, made me think, in general, about all useless powers/skills you can actually have in many RPGs. Supposing enough "good" advancement options exist, is it a problem if a RPG system offers a few of the so-called "traps"? ( i.e, terrible character advancement options, even if sometimes they look good.)
An example often mentioned are the feats in 3.5 that offer a +2 to a skill. Other examples are spells, which lack an apparent practical use.
IMHO: they're fine, I even like the fact they're there. A game isn't better or worse balanced simply because a game has "traps"; it only means players and DM should do their homework. Not to mention pure roleplay usage (especially in PnP, oc), or the fact that maybe there's an unexpected use for that "lame" spell, which even goes beyond what designers had in mind.
I think you need to be wary whenever the term "trap" gets thrown about. IIRC Ever since Monte Cook made that ivory tower essay, butthurt players have been latching onto the word to complain about any skill they think solely exists to punish uninformed players, when it'd be more accurate to be "exists to serve a small niche, but lacks a broad/awshum-button use for my character".
As a counter to the often cited "trap" feats:
Skill bonus: skill bonus (concentration) is a pretty good feat for a low con wizards in the early levels. In PnP the feat can be an a way to represent certain quirks about your char.
Toughness (the +3 hp at level 1 variant): If you know a campaign won't go far beyond lvl 1, it's a pretty nice bump. Double the hp in the wizard's case.
As others have mentioned, there's a danger in trying to balance all the abilities to be equally useful, as you lead to a bland awesome-button game where you can faceroll through everything as the designer had to make sure your special snowflake character feels powerful.
tldr;
Not a trap: Picking weapon specialisation (daggers) and complaining you don't do as much damage compared to spec'ing in longswords. You knew what you was getting yourself in to...
An actual trap: Picking weapon specialisation (longsword), then finding out the only magical weapons are daggers, and you need a +3 weapon to fight that demon overlord.
They've also sucked in HoMM 3, unless you've played the Wake of Gods mod in which they were actually pretty decent.
Anyway Deus Ex had swimming. I don't know a single person who took it in their build.
I never understood this swimming = useless criticism in deus ex. There are are several secrets that can only be reached by having some kind of swimming ability (be it skill, augment, or env. training + rebreather). The swimming skill itself is so low investment I can just put my excess points into getting 1-2 ranks in it and get some nice return from it.