<p>Some favorites:</p>
<ul>
<li><a href="https://math.stackexchange.com/questions/2556169/need-a-trivial-proof-of-an-obvious-combinatorial-result/2561429#2561429">Need a <em>trivial</em> proof of an “obvious” combinatorial result</a></li>
<li><a href="https://math.stackexchange.com/questions/2611424/existence-of-v-subset-mathbbrn-v-v-perp-cap-mathbbr-geq0n-0/2617109#2617109">Existence of <span class="math-container">$V\subset\mathbb{R}^n:V,V^\perp\cap\mathbb{R}^n_{\geq 0}=0$</span></a></li>
</ul>

Yly