Something cheap and hassle free, I think the Kindle Fire is an easy choice. It's got a nice dual core processor (better than Tegra 2 found in most tablets at the moment), though only 512MB of RAM and 8GB of storage (about 6GB available to the user). But includes the Amazon Appstore, not as large as Google's Market, but still pretty decent sized and typically should be able to find all the good apps and games.
Nook Tablet would be good if you don't mind some hassle. Appears to have the same processor, but also 1GB of RAM and a micro SD slot. Down side is the Nook Store sucks for games. So you or he'd want to root this thing and load the Google Market at least. Even just rooted and Google apps loaded, it pretty much becomes a fully functional tablet. And rooting shouldn't be too difficult. I just happen to hate the look of the device myself. But great value if you root it.
Samsung Galaxy Tab 7.0 Plus looks very awesome, as someone recommended. But at $400, probably more than you want to spend.
A used or refurbished Transformer would be really nice. Imagine there might be quite a few available soon with the Transformer Prime launching in early December.