Pass the pigs is a strangely addictive game where you replace liar dice with two little pigs. You shake the cup and roll the pigs. Depending on how the pigs fall, you win points, win the game or snout out. The more experienced players will know all about throwing a sider and getting a leaning jowler. Weird but fun. Very portable so you can play it anywhere. Excellent for staycations when it's raining. Good for 2 or more players 8+.
Eleven year old boys are still boys rather than teenagers. A super soaker water gun is still a great present for an 11 year old, but if they are getting seriously into cool, a cool piece of room decoration might be welcome. Construction kits that involve the opportunity to build cool, outlandish models are popular. Wicked Uncle has everything from a classic chess set to a DNA Experiment Kit. No problem getting a great present. And even big boys like cool toys.