What game should I get? (low end PC specs)

Posting your PC specifications would be really helps.

Both AC3 and FarCry 3 have high requirements, but as an AC fan, imma recommend you to get Assassin's Creed.

Minecraft, Runescape. Maybe something off of Miniclips.

Well, if it's still as buggy as it was at launch, AC3 is the most demanding one. Due to the fact it was a terrible port. People were getting 10 frames/sec in the cities on the lowest settings, even though they exceeded the recommended requirements.

Far Cry 3, it is really optimized. I ran it well on an old core 2 duo 1.86 ghz on low-med settings

Diablo 3

Well, my lappy is not that good and I can run Far Cry 3 pretty well.

Despite what else anyone here will say - your GPU really is a HUGE bottleneck here, and neither of the two games (FC3 / AC3) will run on it, I guarantee it.

I had a GT430, and the card had HUGE trouble keeping up with any games that demanded more than, say, a Source engine game. Most newer games flat-out didn't work on it. Are you sure it's a GT240? And not a GTX240?

Try some games on Nitrome. I found some short & awesome games on there. They also have a game on greenlight if you're interested.

wut

try crysis 3

Terraria.

Half life 1 and 2 best games and low requirements

Lol. Forget about those games and play Bioshock 1.

I guess you should choose AC3, but I'm not entirely sure... If you're into editing configuration files, Far Cry 3 is the better choice by FAR.

They're both awesome games, prepare for a lot of hate on AC3 though, a lot of people really dislike the game for whatever reason.

If you're already played up to Revelations I would go for Far cry 3 though, just to have a different kind of game in your library, take a break from Assassin's Creed for a bit then buy AC3 later on when it's on sale or something.