Looking at a lot of the drops, there are a couple of things that really have looked to benefit.
Nidoking: No Chansey makes it the premier wallbreaker in UU. Virtually no Stall core is going to beat it when it runs Sludge Wave, Earth Power, Focus Blast, and Thunderbolt / Fire Blast. It drops Florges, Umbreon, Forretress, Tentacruel, Empoleon, and many others. About the only 2 defensive Pokemon that really have a chance off the top of my head are AV Escavalier and AV Slowbro... and that depends on the 4th move Nidoking runs. Serious threat to every stall team now imo.
Mega Ampharos: It is now the best offensive-inclined answer to Tornadus-T, Crawdaunt, and most other Electric-types. It has the bulk to check Starmie and OHKO it, and is one of the few slower Pokemon that denies Salamence and Haxorus a switch-in with the threat of Dragon Pulse. It does have some issues with Salamence once it does switch-in, but considering M-Ampharos is already great with Florges and AV Slowbro, this shouldn't be a major concern.
Empoleon: With Latias and Zapdos gone, Empoleon is about the only defensive Defog user remaining. It has good special bulk and solid Special Attack to make many opposing threats think twice before switching in. Assault Vest lost even more value now that Zapdos is gone, but it also doesn't have to worry about Keldeo anymore. Mixed bag, but overall, I think Empoleon won.
Vaporeon: While not appearing to win at first, Keldeo was the biggest roadblock to Vaporeon running a Specs set. With no more Keldeo, it's highly possible that Vaporeon's old DPP Choice Specs set could make a comeback in XY UU. Chansey leaving the tier only opens this door even more. Tentacruel is a hard counter to her now though while defensive sets can do very little to Trevenant. (all the more reason to run Specs) However, defensive sets can also run Ice Beam to check Salamence now, so that's a plus.
Raikou: Look out for this beast. Remember the beast that was SubCM Raikou last generation? Chansey leaving just made it viable again. It outpaces Salamence, rocks Tentacruel's world, and can simply blast through Klefki and Sableye with more offensive sets. Zapdos leaving makes Choice Specs Raikou incredibly dangerous since it won't have to compete with the harder hitting Zapdos (Magnezone is super slow), so look out. AV sets got a bit more viable as well with Starmie entering the tier as the AV boost will make Speed ties much less risky.