What level are they at? I have done a few and am trying to think what actually worked. I think whatever you do the main thing is to actually review the TB events and what people learnt rather than just go back to their desks after it. And they rally only work if there are at least a few people who are committed to getting something out of it.
one I can remember is to get a ball of string and start off by passing it to someone in the team who you rely on and explain why. So you would pass it to the admin person and say without them you could not get the letters out. They then pass it to the phone person and say without them they would not get the details to write the letters. This goes on and on until everyone is joined together by lots of string. Cue your lecture about how everyone works togeher etc etc.
Or ask each member of the team to tell you somrthing about themselves that their colleagues should know ie if they have children, pets etc. then create a team quiz with a mixure of these personal questions, work related qauestions and general knowledge. IME everyone loves quizes and you could even split the team into 2 or run a challenge against another team in the company.
Give everyone in he team a peice of A4 paper and each person writes their name at the top. The paper gets passed round the team and everyone has to write one positive thing about the person whose name it at the top, it can be anything from has really nice hair to something work related. Each time the paper gets folded over and passed to the next person and so on. When the original person gets their paper back they get to read nice things that their team have written about them and feel valued etc.
Or, arrange a team lunch but everyone has to make or bring something themselves.
Could you set some team targets around productivity and quality with a meaningful reward at the end? It works well if people are willing to work together and create some unity and help each other suceed.
And finally, agree with going to the pub and getting drunk. I think you are far more likely to work well with someone you know and like.
I will try to find my old books on teambuilding and get some other ideas, but god knows where they all are.