Latios Ex can fit in EVERYTHING that wants a Latilock. Everything having a spare space or two can reconsider it.
Rayquaza COULD go in a lot of decks with d Rainbow Energy, Electric energy or Holon Pokes but too bad you can't mentor him.
Mew is always a cool tech, but doesn't fit everywhere sadly.
Lugia...only if you got energy accelerators and energy movement imho.
Absol isnt a tech. Its something you use in your deck to enhance the preformance, not just splash in, and only in decks that spread a lot of damage.