::first-letter

p::first-letter {
  font-size: 1.5rem;
  font-weight: bold;
  color: brown;
}

<p>
  Scientists exploring the depths of Monterey Bay unexpectedly encountered a
  rare and unique species of dragonfish. This species is the rarest of its
  species.
</p>

<p>
  When Robison and a team of researchers discovered this fish, they were aboard
  a week-long expedition.
</p>

::first-letter {
  /* ... */
}

<h2>My heading</h2>
<p>
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy
  eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam
  voluptua. At vero eos et accusam et justo duo dolores et ea rebum. Stet clita
  kasd gubergren, no sea takimata sanctus est.
</p>
<p>
  Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie
  consequat.
</p>

p {
  width: 500px;
  line-height: 1.5;
}

h2 + p::first-letter {
  color: white;
  background-color: black;
  border-radius: 2px;
  box-shadow: 3px 3px 0 red;
  font-size: 250%;
  padding: 6px 3px;
  margin-right: 6px;
  float: left;
}

<p>
  Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie
  consequat.
</p>
<p>-The beginning of a special punctuation mark.</p>
<p>_The beginning of a special punctuation mark.</p>
<p>"The beginning of a special punctuation mark.</p>
<p>'The beginning of a special punctuation mark.</p>
<p>*The beginning of a special punctuation mark.</p>
<p>#The beginning of a special punctuation mark.</p>
<p>「特殊的汉字标点符号开头。</p>
<p>《特殊的汉字标点符号开头。</p>
<p>"特殊的汉字标点符号开头。</p>

p::first-letter {
  color: red;
  font-size: 150%;
}

<svg viewBox="0 0 300 40">
  <text y="30">First letter in &lt;text&gt; SVG</text>
</svg>

text {
  font-family: sans-serif;
}

text::first-letter {
  font-family: serif;
  font-size: 2rem;
  font-weight: 600;
  fill: tomato;
  stroke: indigo;
}