My top 3:
1. Any glasses wearers, a quick wash of the specs under the tap with some washing liquid is like a whole new day.
2.Cyclists: get 2 bottle carriers, on short trips use the second carrier to hold a wide neck bottle and shove your keys, phone, etc into it, even a rain jacket if you can afford one that small.
3. The vomiting child. Up to a certain age it's impossible to direct a vomiting child where to release the cargo. When they are exhausted and lying in bed beside you just waiting to spew again, bath towels are your only option, you can cover the projectile area and save the bed.