[quote name='furyk']I play online very rarely actually which is why I have every domestic game with online features besides Tenchu DS, Tony Hawk Downhill Jam, and Mario vs DK 2, but I don't have a single friend code up.[/quote]
You said Tenchu... Oh sweet jesus.
How could you buy that, man. I bought it and took it back in 2 days.
Anyway, about the games that have online feature, there are plenty. Just look for the Wifi logo on the box, but be warned, not all games have a good online feature: some games are better at it than the others.
For one, CV
OR, even though it's a sold game but it can't be denied that its online play is somewhat lackluster. On the other hand, Club House Games may has a not-so-good offline single player but it has a very strong multiplayer (both local and online play... Pictochat online, anyone ?).
So if you want to get a Wifi game, don't buy it just because you see the logo on it, but do search for it on the internet and see the reviews.
These are just my 2 cents.