Lanturn
Lilligant
Cofagrigus
Rotom-C
Lanturn is a team player - it sponges special moves for the team, especially Electric-, Fire-, and Water-type moves, and can provide some paralysis and Heal Bell support. Its slow Volt Switch lets it bring in teammates for free. It's a very useful mon to have on a team.
Nothing sweeps like Lilligant. With Sleep Powder and Quiver Dance boosting its Speed and Special Defense, revenge-killing Lilligant is only done by a select few RU mons. A pokemon that makes Lanturn a liability is a fearsome threat in my eyes.
Cofagrigus is still the #1 spinblocker that also packs a punch with Trick Room and Nasty Plot. Its defensive set is nice for checking physical sweepers, too, I guess, but the OTR is the more noteworthy set imo, since it can pull off sweeps relatively easily. There are many Psychic-mons weak to Ghosts for Cofagrigus to take advantage.
Rotom-C > Slowking, imo. Slowking has too many exploitable weakness in this meta; bug, electric, grass, dark, and ghosts are all prevalent moves in RU. Rotom-C is also a victim of Fire-, Bug-, and Ice-type moves, but it has a niche in its ability to Volt Switch with relative ease. Unlike Manectric and Galvantula, Rotom-C has STAB Leaf Storm to threaten Lanturn and even Nidoqueen from switching in.
Rotom-C also has great stats, with a good balance of power, bulk, and Speed. Granted it's not fast enough to check Moltres and Entei, but it does check sweepers like Feraligatr, Kabutops, Magmortar, and NIDOQUEEN pretty well. It's also a decent check to Lilligant, being able to take a neutral Hidden Power and retaliate with Trick / T-Wave. It's fast enough to be an efficient Scarfer, although it runs the EB set really well, which blarajan introduced to me. With Grass-Fire-Electric offense, it's very hard to safely switch into Rotom-C. Thanks to Volt Switch, good bulk, and versatile offense, Rotom-C makes for a very solid player in RU; not to the same level as Rotom-W in OU, but still damn good.