Here are some pet peeves of mine when it comes to Halloween costumes. If you're tempted to employ any of these, IMO, don't bother "dressing up." For sure don't come to my house asking for candy. I'm more likely to spray you off my porch with a garden hose.
Things that are *NOT* Halloween costumes:
1) Throwing a circa 1990's leather jacket over your white dress shirt and pleated tan Dockers, drumming up a cheap fedora-ish looking hat and calling yourself Indiana Jones.
2) Real life gear (local high school football uniform, dirt bike outfit, hunting camo/orange).
3) Any Halloween-themed t-shirt and/or headband with bats, pumpkins, etc. boinging from springy antennae.
What other weak-sauce costumes am I forgetting?