This is a very flawed but also very threatening special attacker.
Evasive Schemer
Cacturne @ Bright Powder/Wise Glasses
Nature: Modest
Ability: Sand Veil
EVs: 252 SpA / 4Def / 252 Spe
- Nasty Plot
- Dark Pulse
- Focus Blast
- Grass Knot/Energy Ball
As with anything else attempting to sweep, low speed and paper defences do it no favours.
However, it is not lacking in power as basically everything falls to it in at most two hits after a Nasty Plot with the majority being OHKOed.
It will get a few chances to set up as slow Grass weaks or Sucker Punch wary choicers will still run while others locked into inaccurate moves suffer from Sand Veil.
Once it's set up, even the great special wall, Blissey, is 2HKOed by +2 Focus Blast while Curse Snorlax is a likely OHKO with SR (certain with Wise Glasses).
Therefore, slower teams (or teams made slow by paralysis) are dismantled by the appropriate 120 base power move coming off 722 SpA.
It is given a shot against swifter opponents due to the considerable evasion boost granted by Sand Veil and possibly Bright Powder.
Cacturne's best boosting set is generally considered to be the Swords Dance set due to the destructive potential of +2 STAB Sucker Punch.
Sadly, the special attacker misses out on priority but, OTOH, the target cannot evade Dark Pulse by failing to attack and Intimidate is no issue.
So generally, even when you're slower, you'll be attacking and your opponent will be as well while hoping that Sand Veil doesn't do its thing.
Overall, I consider this set to be on the gimmicky side but due to Cacturne's flaws most of its sets have a bit of that aspect.
In fact, I'm guessing that most people who choose to use Cacturne are looking for something hard hitting and different though not necessarily optimal.
Optimal this isn't, but it shares the quality with other Cacturne sets of being damn fun to use (and frustrating to play against!) when it works out.