Small workplace. Tricky dynamics and slight cliquey-ness caused by working days and all being part time. I had a "special" birthday earlier in year - couple of colleagues got me small gifts etc. Now another colleague is having a major age birthday and a collection has been organised. I've been asked to contribute as haven't so far.
Petty/assertive(??) me: don't contribute and buy own separate gift (I like colleague and she did same for me)
EVEN more petty: as above but make it obvious why.
Virtuous and/or walkover: just shut yer face and contribute then stew about it for several years
(I'm actually quite hurt/annoyed about it, it kind of confirms the popularity contest which I've never taken part in and therefore was never going to win)
N.B I can be over-sensitive.