Can anyone suggest some rounds for my 'Challenge Quiz?'

Wacker

Hi folks,

Four of my friends are coming back from their travels in about a month, and I'll be welcoming them home in the same way as I saw them off: by hosting a Challenge Quiz. The first one worked as follows:

1. Divide everyone there (about 20 people) into just two teams, ensuring that no one was on the same team as their better half.
2. Pick captains for the teams, and task them with giving out playing cards with vague challenge categories written on them to their teams. Both teams got the same set of cards, so everyone knows that they're going to be competing directly against one person from the other team.
3. The categories were given names like Physical Endurance 1 or Mental Agility 3, etc. so no one would know what they'd be doing until it's too late!
4. Hold the challenges in no particular order, until they were all done.

It was a resounding success! The first challenge held saw the two unlucky participants having to drink as much salt-water as they would/could in two minutes, with the guy who drank the most/finished his glass first earning a point for his team. So, it had been on for three minutes and I had someone puking! Other challenges were as follows:

Mental Agility: List as many prime numbers as you can in two minutes.
Visual observation: How quickly can you find Wally in an old Wheres Wally book.
Physical Endurance: Using both arms, how long can you keep a 10 lbs dumbbell held out.
Physical Dexterity: both challengers were given half a Jenga set, and they had to build as high a tower as they could in two minutes.

You get the idea. Luckily, it went down to the wire, with the teams neck in neck going into the last round.

Anyway, I'll be hosting another one soon enough, and I need new ideas for challenges.

I've had the following ideas already:
1. Four teams, not two, with the returning people all captains. This means everyone will be doing more challenges, which is good, but it makes the challenges more restrictive.
2. Every team has a card that they must use at one point, when they only know the category of their challenge. It's the 'Wacker Stand-In Card', where I compete for the team instead of their would be challenger!
3. I would love some team-rounds, where the teams have to work together as one. I didn't have that in the last one at all.
4. The last round will be entitled Co-operation, and will feature two challengers per team. One of them will be blindfolded, and the other will have their hands cuffed behind their back, and between them, they'll have to put together the most ludicrously simple toddler's jigsaw! This might be awesome, or it might be way too hard.

So anyway, can any of you intrepid quiz-masters think of any challenges for me? I don't want to spend too much money on this, but I'm prepared to shill out a little. It's just for fun! I want as much variety as possible, so try to mix it up a bit.

Thank you in advance, and feel free to steal my idea!