One of the reasons which endear 'How I Met Your Mother' to its viewers is its impressive array of wacky things that play an integral role to the storylines.  Since the show's timeline does not follow a chronological order, these items are often spotted on screen most especially in the forms of flashbacks.

The Intervention Banner

This is the symbol of the HIMYM gang that they are indeed determined to help each other overcome their fickle habits such as Marshall's excessive usage of charts and Robin's penchant for spray tans.

The Ducky Tie

This perky tie that Barney is forced to wear made viewers remember him more. For most parts of the seventh season, Barney had no choice but to wear the prop after losing a bet with Lily and Marshall.

Marshall's Hat

One of the funny aspects of Marshall and Lily's wedding day is the groom's meltdown which made him shave off a part of his hair. In order to conceal his irrational deed, the gang searched for wigs and even American headdresses. In the end, they opted for a hat which Marshall regretted wearing.

The Blue French Horn

The horn might be trivial but for Ted, it is very significant after stealing it for Robin during their first date. The pair eventually returned the horn to the restaurant which ended in a break up.

The Playbook

Everything you need to know about dating and impressing women is in Barney Stintson's book which is also deemed as one of the show's most iconic props.