I would always recommend separating /var from the others, especially when you're only talking 1% of your total drive space. I don't know why everyone seems to think this is not the case on home systems.
The reason I say this is when a native Linux application encounters a situation (bugs, etc.) that cause it to start logging insane amounts of debugging information, those are generally going to wind up in /var/log. It's not abnormal to see log files grow pretty large (1GB+) in just a few hours, and it's nice to catch those early. You can also run into problems with apps eating up /var/tmp, so it's really best practice to keep that sandboxed off from the rest of the filesystems.
Properly sizing /var is worth the 1% drive space loss to save you a potential headache down the road.
If you're not sure how much to allocate to each partition, you could always go LVM partitions formatted with ext3/4 (or any filesystem that supports online resizing). You'll take a little bit of a disk I/O performance hit, so I don't know that it's a good fit for you with gaming, but it would allow you to create your partitions with what you think you'll need initially, with a pool of free "reserve" space. That space can be used to dynamically grow those partitions on the fly, without even requiring you to unmount the filesystems.
Here's a link you may find interesting if you're curious about that aspect of LVM: