someone in the workplace who will agree to anything and always does what they are told

One who spiritually cooperates with God, based on the dreams or visions one receives from Him—one who is willing to say yes to God's Yes.

your party counterpart that will agree to *anything* regardless of how crazy or stupid - and sometimes illegal - it is, who can meet or beat your intoxication level and still remain as coherent as you are

A yes man is a person who agrees to every opportunity they come across, no matter how crazy it may seem and they do not weigh the consequences.

Yes man(no spoilers) is also a movie that was produced in 2008 starring Jim Carrey. In this movie he makes a conevant with himself to agree to any opportunity that he may come across.

Some people believe they are living life this way by opening up every possible gate to a better future.

Someone who always agrees with authority and does what he's told.

Urban dictionary editors who accept any definition that comes along. It is not known why people do this but theories include:
i) they are attempting to get 100% acceptance stats to look 'kool'
ii) they do not like hurting peoples feelings by saying 'no'
iii) they are dumb

plural: yesmen

someone who always say's they'll be there but either:
1. doesn't turn up, or
2. gives a vague excuse as to why they are going to not show up