I must confess to a weakness for slogan t shirts, particularly as gifts for my family in the USA. Light to send through the post.
My favourite was the one I gave my DD, with a quote from A Midsummer Night's Dream - "Though she be but little she is fierce." DD is the smallest adult in the family and very strong minded!
When I was a very young teenager, I was fond of my t shirt, bought from Private Eye, that said "I love Spotty Muldoon." He was a character created by the late, great Peter Cook. Unfortunately, no one seemed to have heard of Spotty, except my sister and I, so I got some very funny looks whenever I wore it.
What would I have on a t shirt today? Probably" If you voted Tory, it's all your fault. "