Weak & Week

My apologies to any latter-day Mayans out there who don't recognize the image on the right as a calendar.

Might & Mite

Might can be a noun referring to strength, but can also be an auxiliary verb expressing possibility. The guy on the left is showing his might. The guy on the right might, but might not; he's still deciding.
A mite is a tiny little arachnid, but can also generally refer to anything tiny.
"Since many mites are parasitic, it might be wise to not doubt their might."

Muscle & Mussel