Ok so..
Mandatory voting
I think this can get messy. It would require a system to prosecute those who don't vote. That kind of registry can be very easily used for nefarious purposes by politicians or just anyone with access to that information. Also, it would really depend on what degree of mandatory this is. If you get thrown in jail then we are going to see a lot of poor people in prison for no reason. If you get just a fine then we are essentially introducing the inverse of a poll tax. Not voting is a protected form of free speech for a reason and can be interpreted as protest.
Merge house into senate
Last time something like this was posted I got flamed for asking what the point of this one is. The Senate is a representation of the states rights we have in our constitution. It serves as a safeguard against heavily populated areas dictating the laws for much less populated states. I'm all for reform but eliminating the Senate all together seems like a step backwards.
Ban tipping
I think this is another one where the spirit of the idea is right but the execution is wrong. What we need to ban is allowing restaurants to pay tipped positions far below minimum wage, and stop allowing restaurants to take a cut of the tip at all.
The act of tipping itself is a cultural thing that needs to be addressed culturally. If you can't tip someone for something, complications in the law arise that may disallow giving money to people in general. For example how do you distinguish between tipping a server for a meal and giving the server a dollar as a gift?