In no particular order.
1. Disconnect/Deafen (Manectric ex/Dragonite ex d)
2. Psychic Lock/Shield beam (Gardy SW/Jirach ex)
3. Elemental Blast (Lugia ex)
4. Dual Splash/Split bomb (Empoleon/Exeggutor d)...I guess that Fireball bazooka and Spinning tail fall in the same category
5. Mudslide/Flame bluster (Steelix ex/Magmortar lvX)
I know that I am missing a few that were pretty good at their time...
In sets previous to RS there are some attacks worth to mention, like murkrow from Neo, it had an attack that was very anoying, but most old pokemon seem underpowered compared with the new ones.