Word for taking too much pride in something mediocre

Is there a word, preferably pejorative, describing someone who take too much pride in something mediocre?

The reason I'm searching for this word is a good friend of mine constantly dwells on some small achievements, like he'd brag about how he could eat 5 burgers in 5 minutes or how he jogs to work everyday even though it only takes 10 minutes of walking to everyone we meet at the bar. So next time I see him doing that, I want to call him "Stop being (a/an) ____!"

Solution 1:

vainglory, particularly the "inordinate" part of this definition, seems to fit:

Inordinate pride in oneself or one’s achievements

http://www.oxforddictionaries.com/definition/english/vainglory

Solution 2:

How about Boaster

http://www.urbandictionary.com/define.php?term=Boaster

Bragger seems to fit too And please do tell us about their response :)

Solution 3:

If you need a noun, then words like show-off or braggart may suffice. If you need an adjective, smug may help.

Smug

Exhibiting or feeling great or offensive satisfaction with oneself or with one's situation; self-righteously complacent: a smug look; a smug critic.

Ref: Free Dictionary.

Solution 4:

This reminds me of the Dunning-Kruger effect, in that your friend has an undo sense of accomplishment.

To imply anyone who is proud of their accomplishments is actually exhibiting the D-K effect is to imply that it would be difficult to be less accomplished. They're so unaccomplished that they don't even know what accomplishment is.

Telling him he's being Dunning-Kruger would be a big insult. But it may well go over his head.