We bring wine. That way they can choose to use it at the event or keep it as a thank you.
When I say this though I mean it. We have a coeliac in the household and I usually make events gluten free so nothing gets contaminated.
One pet hate though is when I ask people not to bring anything and they bring something (usually with gluten in it) that requires the oven. I'm usually using the oven if I have people over and facilitating this is a hassle.