Magento 2: available field types in system.xml

Magento 2 system configuration provides below fields type.

checkbox,
checkboxes,
column,
date,
editablemultiselect,
editor,
fieldset,
file,
gallery,
hidden,
image,
imagefile,
label,
link,
multiline,
multiselect,
note,
obscure,
password,
radio,
radios,
reset,
select,
submit,
text,
textarea,
time

Looking at the file /lib/internal/Magento/Framework/Data/Form/Element/Factory.php (sources on Github, for Magento 2.2 & 2.3), one can find the following default list of elements, as specified by Amit in his answer:

// Factory.php, lines 26-55
protected $_standardTypes = [
    'button',
    'checkbox',
    'checkboxes',
    'column',
    'date',
    'editablemultiselect',
    'editor',
    'fieldset',
    'file',
    'gallery',
    'hidden',
    'image',
    'imagefile',
    'label',
    'link',
    'multiline',
    'multiselect',
    'note',
    'obscure',
    'password',
    'radio',
    'radios',
    'reset',
    'select',
    'submit',
    'text',
    'textarea',
    'time',
];

If Composer was used to install Magento, the data may also be found in /vendor/magento/framework/Data/Form/Element/Factory.php, as mentioned in Mohit's comment below.