What is on the Bottom of Your Base?

I am an old skool gamer. As such, a large portion of my figure collection is made of metal. Over the years, I have added more and more plastic models, but I found that I really disliked the feel of moving the lighter pieces around the table. 

If you have ever played chess, it is the same notion--Heavy/weighted chess pieces are more enjoyable to use during a game: they are less likely to move/topple over if the table is bumped; and a heavier chess piece feels like a higher quality piece.

So I weight all of my plastic/resin figures. (even tanks!)

Example of different ways to add weight to a figures.

Description of the examples above, From right to left:

1. Aeptus-B uses small bits of lead (like fishing line weights), fills the remaining space with putty, glues on a piece of paper, then paints it.
2. For 40mm bases I will clip everything off the underside of the base and glue a thick metal washer
3. For 25mm bases, I also clip off the underside of the base, but glue a penny to the bottom. I dimly used to use small washers, but they were costing me more than one cent!! Duh!
4. This base isn't weighted, but I had glued a piece of plasticard to the bottom as it seems to sit better on our heavily textured Necromunda terrain.
5. This is a large flying base weighted by 4 pennies. it is magnetized for a Tau Devilfish. This both add weight and lowers the center of gravity.

A penny might not seem like much weight, but it is really hard to tell the difference between a typical human sized metal figure and a weighted plastic figure.

Do you weight your bases? If so, do you use a different process?