What are great counters for SubCM Jirachi and Tornadus in rain and Volcarona in general? If it's possible to use a Pokemon to more that one of these Pokemon, that would be great. :) Thanks!
Well fullblown counters are going to be a little tough to come by, but I can list some checks.
Sub CM Jirachi (rain variant with thunder and water pulse) is stopped cold by Virizon, who can boost up alongside it and win due to resisting both attacks. It'll probably get paralyzed though, which is unfortunate. Breloom is even better, being immune to paralysis. Pysical ground types that can take a water pulse are decent checks assuming they don't waste themselves in confusion, so Swampert is an idea. Overall, I generally just suggest a phazer that isn't OHKO'd by those two moves, unless you're worried about last mon scenarios.
Tornadus in the rain's counters boil down to things that can take it's hurricanes and coverage moves, which isn't a lot. Blissey and chansey can do it, but they need to look out for fighting type coverage. Specially defensive Jirachi is pretty much a hard stop to it, and can paralyze it in return. Tyranitar needs to look out for fighting coverage, but can take hurricanes all day with ease. Finally, anything with strong or super-effective priority can check it with a revenge kill, though bulk up acrobatics variants could be an issue here.
Volcarona is a tricky one, as it comes with various ways to get past all its checks. The pink blobs can wall and defeat variants without recovery, but Morning Sun and Chesto Rest will just set up on them. Heatran can stop those without a super-effective nuetral hidden power, but those with the hidden power can beat even air balloon heatran by popping the balloon first and boosting to absorb heatrans attacks. However, air balloon heatran with rock slide does beat it no matter what, but is very situational. Scarf Terrakion is a fairly good counter, resisting both STABs, but needs to watch out for burns and SE misses. Honestly though, Volcarona is just a tough nut to crack.
Hope that helps!