Most often this is a creature, but stealing planeswalkers, problematic artifacts, or anything else is really handy
Exiling is possible via cards like Chrome Mox, delving it, or hating it via Faerie Macabre
This can usually be found in the bottom corners of the card, but in older card it replaced the set symbol, near the art work
Disadvantages: high volatility, risk of damage or fakes, and the need to track the market
While it requires you to track and remember specific things each turn in order to resolve the trigger in the end step, it does remove the need to disrupt the middle of someones turn to announce triggers in the manner required by cards such as Rhystic Study or Smothering Tithe