I've always enjoyed posing questions to fundie theists that cause them to have to think, a novel experience for many of them.
Not suggesting these are original, or new ... but they rarely fail to get a fun discussion going. Here are my three favs in no particular order:
1. If God created man in his "image," and if by image it means physical likeness, then what does God use his penis for, and on whom?
If by image it means character, since adam and eve were capable of both sin and deception, then God could not be perfectly good since he would share the characteristic of being sinful and deceptive.
2. If God created all living things, then he created bacteria and virus for a purpose. By curing / destroying these creations isn't man destroying that which God created and defying God's will?
And by being innoculated against them, or by using anti-biotics aren't Christians pitting themselves against God's divine plan?
And if you claim God gives man the ability to cure these diseases, how come Jerry Lewis is still raising money to find a cure for Muscular Dystrophy, after 50 years and God doesn't want to give us the answer to the common cold?
And why does God keep creating new diseases to replace the ones he gives us cures for?
3. If God created Earth, and he is omnicient, he must have known that hurricanes, typhoons, earthquakes, et al would killl his innocent and faithful creations. If he knew and still created the earth to allow those things then he is not omnibenevolent, he is malevolent. If he did it by by accident he is not omnicient. If he can't stop them, eliminate them he is not omnipotent. If he can stop it but won't isn't that an indicator he is one evil piece of shit, and no better than Shiva the Destroyer?
My experience is they will excuse themselves and try and find a satisfactory retort from some apologetics site... with terrible results; or they will wing it and invent scripture/doctrine (i.e. "Satan is a creator of bacteria and virus."); or they revert to a completely irrelevant platitude (i.e. "God is good, and this is a wonderful world.")
Try it, see what you get.