Don't give up on a beer too soon. I had a beer several moths ago that tasted horrible with a strange metallic taste to it. I was pretty certain it was infected. Bleached my fermenters and replaced some hoses. Set it aside for a good while and it turned out just fine. Bad flavor disappeared. Can't explain why but it certainly wasn't infected. That was almost a mistake as I was ready to dump it.
I once began adding grain to my kettle before lining it with the BIAB bag. Whoops.
There was one time a few months back where I accidentally left the propane on very low after mash in (my kettle/tun stays on the unlit burner during the mash). Came back after 15 minutes to find it on very low and mash temp now at 156F instead of 148-150F (can't remember exactly what I intended). Any how the beer finished a couple of points higher and was delicious. Not sweet in the least.