For example, on my druid, I don't remember the last time I used Soothe. The other ability I find gathering dust in my spellbook is Hibernate. I know I used Hibernate to help with crowd control for trash packs in Ulduar and Ruby Sanctum during Wrath of the Lich King, but since then? Nope. Hibernate does not live on my bars.
Now, I get that both Soothe and Hibernate have significant uses in PvP, but I really don't PvP, so I don't find either of these spells in my regular rotation. I have both of them bound to click modifiers just in case, but have yet to use them in Mists of Pandaria. For druid talents, I don't personally consider any of them useless, but my personal play style does make some more attractive to me than others. For example, in my feral spec, I currently use Incarnation, though I'm considering switching to Soul of the Forest. Feral is almost exclusively my soloing spec, so the only things I consider when taking feral talents are their convenience to me and getting my questing done, and that extra energy after a finisher looks nice! If I were raiding regularly as feral I'd probably stick with Incarnation for a great opening damage boost, but since I don't, it's not such a priority.
The two other toons I play regularly are both mages (one Horde and one Alliance). My Horde mage is specced arcane, and when I first hit 30 on her I picked Temporal Shield for my tier 2 talent. Boy was that a mistake! All my guildies strongly recommended I switch to Ice Barrier, which I quickly did, and I find it to be an infinitely more useful talent. Temporal Shield? Never again. However, unlike my druid, I have so far yet to encounter a mage spell that I don't regularly use. Now, my mages aren't anywhere near the level cap, but there are certainly no "Soothe" equivalents in their spell books just yet. I haven't decided if that's a blessing or a curse -- check back with me in a few months.
Readers of WoW Insider, are there any talents or abilities that you never use? If so, why don't you use them? Do they just not fit your personal playstyle, or do you feel that your class or spec would genuinely benefit from having them removed and replaced with something else? What would those replacements look like? Let us know!