I'll keep these fishing related just 'cuz it's easier:
Snags that won't come undone.
Sangs that won't come undone with a brand-spankin new lure I just tied on!
That stupid pivot pin on the TM that has almost fallen into the lake about 50 times!
That honest-to-goodness big one that gets within a foot of net range and magically spits the hook!?!
Driving the the lake, staging the boat, just about to get on the ramp, and realizing the plug's on my workbench in the garage! Aaaarrrggghhh!