Found a gem in the uncommon bin of the local game store.
What a great card to be used in a format where creatures have so many triggered effects. A few observations:
1) Nemesis Trap only works on attacking creatures. So unfortunately you will not be able to get rid of utility creatures willy-nilly. Unless your opponent decides to attack you with an Eternal Witness just to be funny. Which he will probably only do once.
2) The clone Nemesis Trap creates lasts exactly one turn. There is no way to use the "end step loophole" to sneakily get it for more than one turn and attack your opponent with his own creature. It's just not going to happen.
3) Nemesis Trap is best used against powerful(important) creatures, or creatures with powerful enter-the-battlefield effects.
4) The target creature is EXILED, so it does end most recursion, unless you are hitting their general.
In my mind, the most effective targets will be Titans and Slivers.
In particular with Slivers, I will probably be facing an onslaught of attackers…and Nemesis Trap will be just what the doctor ordered. The biggest Sliver will be destroyed, while the next baddest Sliver in line will face a copy Sliver just as big.
Unfortunately, the remaining Slivers will still get pumped by my token Sliver…so who knows, maybe I will die anyway!