Stealth Rock - fairly self explanatory. accounts for the viability and inviability of so many pokemon. strategies to put it up, take it out, etc. Hidden Power - how did this topic go this far with no mention of this move? hidden power is the sole reason many pokemon are even usable. Magnezone would be **** without Hidden Power, as would be many special attackers with otherwise lacking coverage options. Volt/Turn - Can't decide on one, so i'll group them together. Major annoyances, but seriously effective means of gaining control of the battle. A big factor in why Genesect is in suspect testing.
After this i'm slightly BSing.
Will-o-Wisp - Residual damage is never fun, but Will-o-wisp does more than just 12.5% per turn. Will-o-wisp's attack drop stops the vast majority of physical attackers dead in their attempts to sweep. Scald is similar to will-o-wisp, but trading the chance to burn for guaranteed immediate damage. Not to mention giving a burn option to bulky water types. Spore - Sleep is annoying, especially with the new sleep mechanics. Spore's guaranteed sleep certainly is rage inducing. Spore takes some otherwise average pokemon and gives them huge utility. Superpower - Fighting is a very strong offensive type. i think this move merits mention due to its wide availability and high power. it's a very effective coverage move that many pokemon love having.