I agree with the others - something edible/single-use (like soap or tea or something) is best. We decided to make ours something that could do double-duty, so we are giving individually wrapped biscuits with peoples' names on them which will also act as the place names.
We are doing hand sanitizer spray as our favor. I bought the 1 oz spray bottles from Amazon. It was like $7.99 per 50 bottles. Then we just got a huge pump of hand sanitizer and added water to help it spray better. I got "Spread Love, Not Germs" stickers from Amazon as well.
We did gourmet butter mints as our favors. We had 120 guests, and around 20 packages were left behind at the end of the night (we did make extras though) so I'd say that most people took them. The few extras were not a problem, because we simply ate them! I would definitely recommend going the edible route if you're going to do favors. Some ideas for favors that can be done very cheaply are M&Ms or Hershey's kisses that you can buy in bulk and wrap in tulle and ribbon if you DIY things
I am in the minority on WW but I love favors!!! I use all of them. Recent ones that went to good use were jars of honey and jars of Cajun spices. I'll be giving out candy boxes at mine
I am very picky about favors. Edible is always a good choice and I can't recall any time I haven't taken an edible favor - even when it's something like macarons (which I don't really like), I will take them just to have something to munch on on the drive home.
But I personally will not take any favor that is reusable and has the couple's name on them. This includes anything like shot glasses, koozies, playing cards, etc. It's hard to explain what my aversion to this is, the only way I can say it is, why would I want shot glasses with other people's names on them in my cabinet? Or why would I use a bottle opener emblazoned with someone else's name? I will always leave these behind.
We had olive oil that was made and packaged by our venue. Everyone loved it! We had a few left over from people that left early or the no-shows. Even the people that left early asked if they could get a bottle. We also had hand sanitizer at the entrance of the ceremony and there was a lot left over which was kinda disappointing, but our families took a bunch and they’ll get used. I ordered the mini bottles from Bath and Body Works, and replaced the sticker with our names and date. They smell really good so it’s not a complete waste!