The ending sequence of the anime has the 3 of them running, with Tohru lagging. One would normally suspect this is because he's a mangaka and he's just unfit. However, the injury mentioned under Friendly Sniper only allows Tohru to run for about 5 minutes before his legs give out. The ED sequence is only about one minute 30 seconds. Simply, if the ED sequence were longer than 5 minutes it would have been a spoiler.
Toy ☆ Gun Gun (トイ ☆ ガンガン in Japanese) may have been named after the online magazine it started out in (ガンガン ONLINE in Japanese).