Some of the early dumb things we argued about:
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Men's inability to ask for directions versus women's tendency to ask sooner than necessary
Socks on the floor
My tendency to leave damp bath towels lying around
Who gets the last four Thin Mint cookies
My using his razor
His getting the soap all hairy
The proper way to brush a cat
Why he cannot follow simple directions at the store and differentiate between Diet Coke and Caffeine Free Diet Coke (my father lacks this ability, too)
Whether or not cheese should be added on top of an omelet or just inside (I wasn't making it the way his mother always did)
Who ate the last of the salsa
Me not remembering to stub checks
Whose turn it was to get up with a sick child
How often I talk to my dad versus he talks to his mother (our respective close-bond and hence most spouse-threatening parents)
Litter-box cleanout frequency
My tendency to be messy and leave things strewn around

Things we still argue about today?
Me not remembering to stub checks
His inability to find/locate items in stores, even with specific instructions
Whose turn it is to let the dogs out (it's generally always mine)
My tendency to be messy