Let's see...
Mud Sport and Water Sport, for reasons mentioned above. XD I'm yet to see a battle where those moves actually make a noticeable difference.
Splash, usually
(except when the totally awesome Magikarp uses it, in which case it results in massive damage).
Snatch would've resulted as a bad move for me, but I'm just now finding out that it works similarly to Psych Up...I hardly saw its use because Elite Four Sidney's Absol typically used the move at the wrong times, in my experience, so I never really figured out what the move does; I rarely saw it in action. Being a TM with limited availability didn't help matters, either.
I
would've said
Rock Smash as well, but that move, when learned by a Grovyle that knows Leer/Screech, is really handy against Wattson's Steel-type Magneton, to my recent surprise - handy when a Pokemon doesn't have many moves to trump Steel-type Pokemon with early on in a game.
Cut still sucks, though, like a lot of low-power moves (DoubleSlap, ).
Prior to Generation 4,
Gust was inferior to Wing Attack (the latter is more powerful, but both share the same Power Points (PP)), until they were made different offensively... I mean, you might as well just let Pokemon learn Wing Attack at the time that Gust is learned...
Fire Spin and similar variants (excluding Magma Storm) - their trapping effect is quite nice, but they seem
much weaker than they should be. A boost in power would be nice...
Self-Destruct, if only because it is weaker than Explosion, and most Pokemon that can learn the former learn the latter anyway.
Egg Bomb - a Physical move; the Pokemon that learn it (Chansey, Blissey, and Exeggutor) are better off using more powerful Special moves. And you might as well teach the aforementioned Return, which has a better maximum power output as well as better accuracy.
I dislike
Barrage for similar reasons as Egg Bomb...Barrage is the signature move of the Exeggcute family, yet it hasn't taken advantage of their higher Special/Special Attack stat since Generation 1. It freaking took Metronome for me to even see this move's animation in Generation 3.
Flash...it just seems like this move
always fails when you use it (my experience with it is mainly in Generation 3). Not to mention that it wastes an HM slot and a moveslot in general.
Protect and its nefarious brethren, Detect and Endure - save for special situations (which you typically have to predict/anticipate, such as a foe using Explosion on the first turn) where it may be useful, this move does nothing but waste my time constantly. Elite Four Phoebe's Level 48 Dusclops is a notorious user of this in
Emerald, as if spamming Protect is its sole/ultimate goal in life. -_-
Spikes - I never really saw the usefulness of this move, and Champion Steven Stone's Skarmory likes to grace me with its animation a lot, yet I keep seeing it mentioned in competitive
Pokemon circles. A rental Forretress had this in Hoenn's Battle Factory, so I tried setting up 3 layers with it, but the damage output was not near the yield I expected at all... I think I'd be much better just attacking with other moves, if the moveset isn't a paltry collection of moves... Toxic Spikes and Stealth Rock seem much more useful, though.
Scary Face - if my Pokemon is really fast, this move is essentially a free turn for me. Even with slower Pokemon that this move might actually have a noticeable effect on, the foe usually goes down in the same turn, or 1-2 turns afterwards. String Shot may count, but that's usually early on in-game, where it's kinda "free turn"-ish but can also have a noticeable effect on low-level Pokemo.
Bone Rush - seems pointless with the existence of Bonemerang and Earthquake (and Marowak learns all 3 of these aforementioned moves).
Charm - when this is used on my Pokemon, either my active Pokemon attacks with moves dependent on Special Attack, or my active Pokemon has so much Attack that it hardly matters. Growl may count as a "bad move", but I usually encounter that early on in-game (where it
does matter, as most low-level Pokemon usually only have access to weak Physical moves like Tackle, Scratch, and Pound).
Iron Tail - I love the concept, name, and the animation of the move, but it just misses
so dang much!
Memento - when the opponent can just switch Pokemon to nullify the stat drops, this move really isn't that great, compared to other similar moves with potential uses like Lunar Dance. Major laughs abound when this move happens to be used on a Pokemon with the Ability, Clear Body. {XD}
Helping Hand - what does this move do again? Every time I see it used (usually by a Plusle/Minun), I'm like "Thank God, a free turn!" It's even worse (for the computer player(s), that is) when
both foes use it in a Double Battle. Now that I've read its actual effect, I think it
might have use in certain situations..
Odor Sleuth/Foresight - that is, when they're used multiple times on the same Pokemon. Usually, the computer's ineptness causes this...
Struggle Bug - probably one of my most detested moves, if only because its English name sounds weird, it wasted the TM slot that could've been allotted to Stealth Rock or another useful move, and it's a move that is weak in power...
Fusion Flare/Fusion Bolt used by Reshiram/Zekrom - The only time Fusion Flare/Cross Flame
might be useful IMO is if you're attacking a Black Kyurem that has used Fusion Bolt... Otherwise, I really don't think that these moves should be used against Dragon-type Pokemon (where their use is encouraged/necessitated)...I mean, really, it just hits for "Not very effective" damage anyway!
The yin-yang thing is kind of nice, but the situational "double the power!" effect of Fusion Flare/Fusion Bolt would've worked just as well on Blue Flare/Freeze Bolt (overkill maybe?). For the most part, I'd prefer that each Pokemon just have
one signature move; it just seems like Fusion Flare/Fusion Bolt took up space where 2 other new moves could've been introduced.
I imagine most players are just going to dump the more powerful Blue Flare and Bolt Strike on Reshiram and Zekrom, anyway... Since Kyurem doesn't recieve Blue Flare and Bolt Strike by changing Formes, Fusion Flare/Fusion Bolt seem a bit more useful as a reliable STAB move.
Sky Attack, Ice Burn, and Freeze Bolt - moves with awesome names and power, but the required charging turn prior to the actual attack detracts from their usefulness. I kind of wish they could be clones of Aeroblast or Earthquake, or receive some other modification that makes them balanced, powerful one-turn moves...
SonicBoom - it's weak (unless the battle involves low-level Pokemon where 20 HP is a decent chunk of the Pokemon's maximum HP), and it took dibs on the much cooler name that the likely more powerful Generation 6 move, Boomburst,
should've used...
Mist Ball/
Luster Purge - if you're going to give a Pokemon a signature move (in this case, Latias and Latios, respectively), at least give them a reason to use it. These moves' names and animations are cool, but they pale in comparison to Psychic's higher Base Power (Psychic's 95, compared to the 70 of Mist Ball and Luster Purge), and I would guess that you're better off just using Psychic for Psychic-type coverage. The only advantage of Mist Ball/Luster Purge IMO is the increased chance of causing stat drops in Special Attack and Special Defense, respectively, but as these moves only have 5 Power Points (PP), that drop may or may not get be used...
I'm not sure how to enhance the moves while keeping them balanced...maybe increase the power of each move to 95 while retaining a 50% chance for stat drops; or boost the move to 80 or 85 while guaranteeing the stat drops with each use... My dream would be these moves with 95 or 100 base power with the same Power Points as Psychic, while retaining the 50% chance for drops (or perhaps guaranteeing the drops...? {<3}) In any case, I just
really want a good competitive reason to use these 2 moves over Psychic when I send out a Lati@s...
And, by the post-game, most attacking moves with a Base Power below 60 aren't really appealing to me... I get that they're there to (partially) prevent overkill early on in the game, but they just seem to waste space by the time you get to the more powerful moves... And when something like Brawly's Meditite gets
Focus Punch in
Emerald (in Generation 3: base power 150, Accuracy 100, provided that it hits) during the battle for the
2nd Badge in the game (at a time when the player is likely to utilize a turn to heal other Pokemon in the party or attempt to set up with an attack-boosting or stat-lowering move; AKA
major punishment if you don't expect Focus Punch), you might as well let players start with Normal-type moves with base 60 power that hit reliably (basically, stuff to replace Tackle).