Sublime user Key-map for Auto-pairing underscores, asterisks & back ticks - just highlight something and press underscore, asterisk or back-tick; really handy for writing content in Markdown or reStructuredText.

Default (linux).sublime-keymap

[
    // Auto-pair underscores
    { "keys": ["_"], "command": "insert_snippet", "args": {"contents": "_$0_"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^(?:\t| |\\)|]|\\}|>|$)", "match_all": true },
            { "key": "preceding_text", "operator": "not_regex_contains", "operand": "[_a-zA-Z0-9_]$", "match_all": true },
            { "key": "eol_selector", "operator": "not_equal", "operand": "string.quoted.underscore", "match_all": true }
        ]
    },
    { "keys": ["_"], "command": "insert_snippet", "args": {"contents": "_${0:$SELECTION}_"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": false, "match_all": true }
        ]
    },
    { "keys": ["_"], "command": "move", "args": {"by": "characters", "forward": true}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^_", "match_all": true }
        ]
    },
    { "keys": ["backspace"], "command": "run_macro_file", "args": {"file": "Packages/Default/Delete Left Right.sublime-macro"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "preceding_text", "operator": "regex_contains", "operand": "_$", "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^_", "match_all": true }
        ]
    },
    // Auto-pair asterisks
    { "keys": ["*"], "command": "insert_snippet", "args": {"contents": "*$0*"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^(?:\t| |\\)|]|\\}|>|$)", "match_all": true },
            { "key": "preceding_text", "operator": "not_regex_contains", "operand": "[_a-zA-Z0-9_]$", "match_all": true },
            { "key": "eol_selector", "operator": "not_equal", "operand": "string.quoted.underscore", "match_all": true }
        ]
    },
    { "keys": ["*"], "command": "insert_snippet", "args": {"contents": "*${0:$SELECTION}*"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": false, "match_all": true }
        ]
    },
    { "keys": ["*"], "command": "move", "args": {"by": "characters", "forward": true}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^*", "match_all": true }
        ]
    },
    { "keys": ["backspace"], "command": "run_macro_file", "args": {"file": "Packages/Default/Delete Left Right.sublime-macro"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "preceding_text", "operator": "regex_contains", "operand": "*$", "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^*", "match_all": true }
        ]
    },
    // Auto-pair backticks
    { "keys": ["`"], "command": "insert_snippet", "args": {"contents": "`$0`"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^(?:\t| |\\)|]|\\}|>|$)", "match_all": true },
            { "key": "preceding_text", "operator": "not_regex_contains", "operand": "[`a-zA-Z0-9`]$", "match_all": true },
            { "key": "eol_selector", "operator": "not_equal", "operand": "string.quoted.backtick", "match_all": true }
        ]
    },
    { "keys": ["`"], "command": "insert_snippet", "args": {"contents": "`${0:$SELECTION}`"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": false, "match_all": true }
        ]
    },
    { "keys": ["`"], "command": "move", "args": {"by": "characters", "forward": true}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^`", "match_all": true }
        ]
    },
    { "keys": ["backspace"], "command": "run_macro_file", "args": {"file": "Packages/Default/Delete Left Right.sublime-macro"}, "context":
        [
            { "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
            { "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
            { "key": "preceding_text", "operator": "regex_contains", "operand": "`$", "match_all": true },
            { "key": "following_text", "operator": "regex_contains", "operand": "^`", "match_all": true }
        ]
    }
]