Same here. I don't really carry any work essentials though. Typically, it's my gloves, or blackberry that I remember are gone. I'm not reclimbing my hill for either of those though.

Depends on whether or not pants are considered essential.

Bra - which is why I have a nice jacket in my cubicle at all times for disguise/cover up.
Shirt - see above.
Belt - not a huge issue, but it's annoying.
Work badge/pass - simply park bike on the exterior rack.
Regular Glasses - I usually wear prescription sunglasses to work, and only once did I forget my regular glasses. I had to wear my sunglasses all day and ended up with a headache by the end of the day. This was at a new job too, so my co-workers all thought I was nuts.
Normal shoes - nuff said.

All that and I do pack my bag at night. This will jinx me somehow...

I forgot my pants once. Had to turn around and get them. I rode 60 miles that day.

Worst I've forgotten so far is a hair brush.

I keep the phone, wallet, id card, etc, in a ziplock. It gets packed the night before. Same with the towel and washcloth. Shampoo and such is in another ziplock.

Socks, shoes, underwear, belt get packed the night before as well.

When I get up I roll up the pants and shirt and pack them and away I go.

If I tried to do all this in the morning I would always be forgetting something.

Lunch.

Too often to mention.

Forgot my laptop. I had to have my wife bring it to me.

Actually yesterday! We went on a hike Sunday, I packed my blackberry and pager in my day pack since I was on call technically. For what ever reason I took my thumb drive, external USB hard drive and headphones out of my pannier too. Needless to say I left home with out the thumb drive, hard drive, headphones, blackberry and pager, oh and my belt. This didn't occur to me until I was about 3/4 of a mile away from home.

The belt, phone, pager, and thumb drive I could do with out. Not having my music and headphones would probably drive me crazy. I turned around and sprinted back home and picked up the forgotten gear :>